forked from Minki/linux
3f9f0aa687
This removes a number of silly games around strncpy_from_user() in
do_getname(), and removes that helper function entirely. We instead
make getname_flags() just use strncpy_from_user() properly directly.
Removing the wrapper function simplifies things noticeably, mostly
because we no longer play the unnecessary games with segments (x86
strncpy_from_user() no longer needs the hack), but also because the
empty path handling is just much more obvious. The return value of
"strncpy_to_user()" is much more obvious than checking an odd error
return case from do_getname().
[ non-x86 architectures were notified of this change several weeks ago,
since it is possible that they have copied the old broken x86
strncpy_from_user. But nobody reacted, so .. See
http://www.spinics.net/lists/linux-arch/msg17313.html
for details ]
Cc: linux-arch@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
3492 lines
84 KiB
C
3492 lines
84 KiB
C
/*
|
|
* linux/fs/namei.c
|
|
*
|
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* Copyright (C) 1991, 1992 Linus Torvalds
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|
*/
|
|
|
|
/*
|
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* Some corrections by tytso.
|
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*/
|
|
|
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/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
|
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* lookup logic.
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*/
|
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/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
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*/
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|
|
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#include <linux/init.h>
|
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#include <linux/export.h>
|
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/namei.h>
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#include <linux/pagemap.h>
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#include <linux/fsnotify.h>
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#include <linux/personality.h>
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#include <linux/security.h>
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#include <linux/ima.h>
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#include <linux/syscalls.h>
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#include <linux/mount.h>
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#include <linux/audit.h>
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#include <linux/capability.h>
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#include <linux/file.h>
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#include <linux/fcntl.h>
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#include <linux/device_cgroup.h>
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#include <linux/fs_struct.h>
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#include <linux/posix_acl.h>
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#include <asm/uaccess.h>
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|
|
|
#include "internal.h"
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|
#include "mount.h"
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|
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/* [Feb-1997 T. Schoebel-Theuer]
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* Fundamental changes in the pathname lookup mechanisms (namei)
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* were necessary because of omirr. The reason is that omirr needs
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* to know the _real_ pathname, not the user-supplied one, in case
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* of symlinks (and also when transname replacements occur).
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*
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* The new code replaces the old recursive symlink resolution with
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* an iterative one (in case of non-nested symlink chains). It does
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* this with calls to <fs>_follow_link().
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* As a side effect, dir_namei(), _namei() and follow_link() are now
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* replaced with a single function lookup_dentry() that can handle all
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* the special cases of the former code.
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*
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* With the new dcache, the pathname is stored at each inode, at least as
|
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* long as the refcount of the inode is positive. As a side effect, the
|
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* size of the dcache depends on the inode cache and thus is dynamic.
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*
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* [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
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* resolution to correspond with current state of the code.
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*
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* Note that the symlink resolution is not *completely* iterative.
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* There is still a significant amount of tail- and mid- recursion in
|
|
* the algorithm. Also, note that <fs>_readlink() is not used in
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* lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
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* may return different results than <fs>_follow_link(). Many virtual
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* filesystems (including /proc) exhibit this behavior.
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*/
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|
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/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
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* New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
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* and the name already exists in form of a symlink, try to create the new
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* name indicated by the symlink. The old code always complained that the
|
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* name already exists, due to not following the symlink even if its target
|
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* is nonexistent. The new semantics affects also mknod() and link() when
|
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* the name is a symlink pointing to a non-existent name.
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*
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* I don't know which semantics is the right one, since I have no access
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* to standards. But I found by trial that HP-UX 9.0 has the full "new"
|
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* semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
|
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* "old" one. Personally, I think the new semantics is much more logical.
|
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* Note that "ln old new" where "new" is a symlink pointing to a non-existing
|
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* file does succeed in both HP-UX and SunOs, but not in Solaris
|
|
* and in the old Linux semantics.
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|
*/
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|
|
|
/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
|
|
* semantics. See the comments in "open_namei" and "do_link" below.
|
|
*
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|
* [10-Sep-98 Alan Modra] Another symlink change.
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|
*/
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|
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|
/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
|
|
* inside the path - always follow.
|
|
* in the last component in creation/removal/renaming - never follow.
|
|
* if LOOKUP_FOLLOW passed - follow.
|
|
* if the pathname has trailing slashes - follow.
|
|
* otherwise - don't follow.
|
|
* (applied in that order).
|
|
*
|
|
* [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
|
|
* restored for 2.4. This is the last surviving part of old 4.2BSD bug.
|
|
* During the 2.4 we need to fix the userland stuff depending on it -
|
|
* hopefully we will be able to get rid of that wart in 2.5. So far only
|
|
* XEmacs seems to be relying on it...
|
|
*/
|
|
/*
|
|
* [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
|
|
* implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
|
|
* any extra contention...
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|
*/
|
|
|
|
/* In order to reduce some races, while at the same time doing additional
|
|
* checking and hopefully speeding things up, we copy filenames to the
|
|
* kernel data space before using them..
|
|
*
|
|
* POSIX.1 2.4: an empty pathname is invalid (ENOENT).
|
|
* PATH_MAX includes the nul terminator --RR.
|
|
*/
|
|
static char *getname_flags(const char __user *filename, int flags, int *empty)
|
|
{
|
|
char *result = __getname(), *err;
|
|
int len;
|
|
|
|
if (unlikely(!result))
|
|
return ERR_PTR(-ENOMEM);
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|
|
|
len = strncpy_from_user(result, filename, PATH_MAX);
|
|
err = ERR_PTR(len);
|
|
if (unlikely(len < 0))
|
|
goto error;
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|
|
|
/* The empty path is special. */
|
|
if (unlikely(!len)) {
|
|
if (empty)
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|
*empty = 1;
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|
err = ERR_PTR(-ENOENT);
|
|
if (!(flags & LOOKUP_EMPTY))
|
|
goto error;
|
|
}
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|
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|
err = ERR_PTR(-ENAMETOOLONG);
|
|
if (likely(len < PATH_MAX)) {
|
|
audit_getname(result);
|
|
return result;
|
|
}
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|
|
|
error:
|
|
__putname(result);
|
|
return err;
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|
}
|
|
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|
char *getname(const char __user * filename)
|
|
{
|
|
return getname_flags(filename, 0, NULL);
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|
}
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|
|
|
#ifdef CONFIG_AUDITSYSCALL
|
|
void putname(const char *name)
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|
{
|
|
if (unlikely(!audit_dummy_context()))
|
|
audit_putname(name);
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|
else
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|
__putname(name);
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|
}
|
|
EXPORT_SYMBOL(putname);
|
|
#endif
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|
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|
static int check_acl(struct inode *inode, int mask)
|
|
{
|
|
#ifdef CONFIG_FS_POSIX_ACL
|
|
struct posix_acl *acl;
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|
|
|
if (mask & MAY_NOT_BLOCK) {
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|
acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
|
|
if (!acl)
|
|
return -EAGAIN;
|
|
/* no ->get_acl() calls in RCU mode... */
|
|
if (acl == ACL_NOT_CACHED)
|
|
return -ECHILD;
|
|
return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
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|
}
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|
|
|
acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
|
|
|
|
/*
|
|
* A filesystem can force a ACL callback by just never filling the
|
|
* ACL cache. But normally you'd fill the cache either at inode
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|
* instantiation time, or on the first ->get_acl call.
|
|
*
|
|
* If the filesystem doesn't have a get_acl() function at all, we'll
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|
* just create the negative cache entry.
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|
*/
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|
if (acl == ACL_NOT_CACHED) {
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|
if (inode->i_op->get_acl) {
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|
acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
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|
if (IS_ERR(acl))
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|
return PTR_ERR(acl);
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|
} else {
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|
set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
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|
return -EAGAIN;
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|
}
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|
}
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|
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|
if (acl) {
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|
int error = posix_acl_permission(inode, acl, mask);
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|
posix_acl_release(acl);
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|
return error;
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|
}
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|
#endif
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|
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|
return -EAGAIN;
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|
}
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|
|
|
/*
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|
* This does the basic permission checking
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|
*/
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|
static int acl_permission_check(struct inode *inode, int mask)
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|
{
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|
unsigned int mode = inode->i_mode;
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if (current_user_ns() != inode_userns(inode))
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goto other_perms;
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|
if (likely(current_fsuid() == inode->i_uid))
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|
mode >>= 6;
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else {
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|
if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
|
|
int error = check_acl(inode, mask);
|
|
if (error != -EAGAIN)
|
|
return error;
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|
}
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|
|
|
if (in_group_p(inode->i_gid))
|
|
mode >>= 3;
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|
}
|
|
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|
other_perms:
|
|
/*
|
|
* If the DACs are ok we don't need any capability check.
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|
*/
|
|
if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
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|
return 0;
|
|
return -EACCES;
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|
}
|
|
|
|
/**
|
|
* generic_permission - check for access rights on a Posix-like filesystem
|
|
* @inode: inode to check access rights for
|
|
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
|
|
*
|
|
* Used to check for read/write/execute permissions on a file.
|
|
* We use "fsuid" for this, letting us set arbitrary permissions
|
|
* for filesystem access without changing the "normal" uids which
|
|
* are used for other things.
|
|
*
|
|
* generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
|
|
* request cannot be satisfied (eg. requires blocking or too much complexity).
|
|
* It would then be called again in ref-walk mode.
|
|
*/
|
|
int generic_permission(struct inode *inode, int mask)
|
|
{
|
|
int ret;
|
|
|
|
/*
|
|
* Do the basic permission checks.
|
|
*/
|
|
ret = acl_permission_check(inode, mask);
|
|
if (ret != -EACCES)
|
|
return ret;
|
|
|
|
if (S_ISDIR(inode->i_mode)) {
|
|
/* DACs are overridable for directories */
|
|
if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
|
|
return 0;
|
|
if (!(mask & MAY_WRITE))
|
|
if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
|
|
return 0;
|
|
return -EACCES;
|
|
}
|
|
/*
|
|
* Read/write DACs are always overridable.
|
|
* Executable DACs are overridable when there is
|
|
* at least one exec bit set.
|
|
*/
|
|
if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
|
|
if (ns_capable(inode_userns(inode), CAP_DAC_OVERRIDE))
|
|
return 0;
|
|
|
|
/*
|
|
* Searching includes executable on directories, else just read.
|
|
*/
|
|
mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
|
|
if (mask == MAY_READ)
|
|
if (ns_capable(inode_userns(inode), CAP_DAC_READ_SEARCH))
|
|
return 0;
|
|
|
|
return -EACCES;
|
|
}
|
|
|
|
/*
|
|
* We _really_ want to just do "generic_permission()" without
|
|
* even looking at the inode->i_op values. So we keep a cache
|
|
* flag in inode->i_opflags, that says "this has not special
|
|
* permission function, use the fast case".
|
|
*/
|
|
static inline int do_inode_permission(struct inode *inode, int mask)
|
|
{
|
|
if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
|
|
if (likely(inode->i_op->permission))
|
|
return inode->i_op->permission(inode, mask);
|
|
|
|
/* This gets set once for the inode lifetime */
|
|
spin_lock(&inode->i_lock);
|
|
inode->i_opflags |= IOP_FASTPERM;
|
|
spin_unlock(&inode->i_lock);
|
|
}
|
|
return generic_permission(inode, mask);
|
|
}
|
|
|
|
/**
|
|
* inode_permission - check for access rights to a given inode
|
|
* @inode: inode to check permission on
|
|
* @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
|
|
*
|
|
* Used to check for read/write/execute permissions on an inode.
|
|
* We use "fsuid" for this, letting us set arbitrary permissions
|
|
* for filesystem access without changing the "normal" uids which
|
|
* are used for other things.
|
|
*
|
|
* When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
|
|
*/
|
|
int inode_permission(struct inode *inode, int mask)
|
|
{
|
|
int retval;
|
|
|
|
if (unlikely(mask & MAY_WRITE)) {
|
|
umode_t mode = inode->i_mode;
|
|
|
|
/*
|
|
* Nobody gets write access to a read-only fs.
|
|
*/
|
|
if (IS_RDONLY(inode) &&
|
|
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
|
|
return -EROFS;
|
|
|
|
/*
|
|
* Nobody gets write access to an immutable file.
|
|
*/
|
|
if (IS_IMMUTABLE(inode))
|
|
return -EACCES;
|
|
}
|
|
|
|
retval = do_inode_permission(inode, mask);
|
|
if (retval)
|
|
return retval;
|
|
|
|
retval = devcgroup_inode_permission(inode, mask);
|
|
if (retval)
|
|
return retval;
|
|
|
|
return security_inode_permission(inode, mask);
|
|
}
|
|
|
|
/**
|
|
* path_get - get a reference to a path
|
|
* @path: path to get the reference to
|
|
*
|
|
* Given a path increment the reference count to the dentry and the vfsmount.
|
|
*/
|
|
void path_get(struct path *path)
|
|
{
|
|
mntget(path->mnt);
|
|
dget(path->dentry);
|
|
}
|
|
EXPORT_SYMBOL(path_get);
|
|
|
|
/**
|
|
* path_put - put a reference to a path
|
|
* @path: path to put the reference to
|
|
*
|
|
* Given a path decrement the reference count to the dentry and the vfsmount.
|
|
*/
|
|
void path_put(struct path *path)
|
|
{
|
|
dput(path->dentry);
|
|
mntput(path->mnt);
|
|
}
|
|
EXPORT_SYMBOL(path_put);
|
|
|
|
/*
|
|
* Path walking has 2 modes, rcu-walk and ref-walk (see
|
|
* Documentation/filesystems/path-lookup.txt). In situations when we can't
|
|
* continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
|
|
* normal reference counts on dentries and vfsmounts to transition to rcu-walk
|
|
* mode. Refcounts are grabbed at the last known good point before rcu-walk
|
|
* got stuck, so ref-walk may continue from there. If this is not successful
|
|
* (eg. a seqcount has changed), then failure is returned and it's up to caller
|
|
* to restart the path walk from the beginning in ref-walk mode.
|
|
*/
|
|
|
|
/**
|
|
* unlazy_walk - try to switch to ref-walk mode.
|
|
* @nd: nameidata pathwalk data
|
|
* @dentry: child of nd->path.dentry or NULL
|
|
* Returns: 0 on success, -ECHILD on failure
|
|
*
|
|
* unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
|
|
* for ref-walk mode. @dentry must be a path found by a do_lookup call on
|
|
* @nd or NULL. Must be called from rcu-walk context.
|
|
*/
|
|
static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
|
|
{
|
|
struct fs_struct *fs = current->fs;
|
|
struct dentry *parent = nd->path.dentry;
|
|
int want_root = 0;
|
|
|
|
BUG_ON(!(nd->flags & LOOKUP_RCU));
|
|
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
|
|
want_root = 1;
|
|
spin_lock(&fs->lock);
|
|
if (nd->root.mnt != fs->root.mnt ||
|
|
nd->root.dentry != fs->root.dentry)
|
|
goto err_root;
|
|
}
|
|
spin_lock(&parent->d_lock);
|
|
if (!dentry) {
|
|
if (!__d_rcu_to_refcount(parent, nd->seq))
|
|
goto err_parent;
|
|
BUG_ON(nd->inode != parent->d_inode);
|
|
} else {
|
|
if (dentry->d_parent != parent)
|
|
goto err_parent;
|
|
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
|
|
if (!__d_rcu_to_refcount(dentry, nd->seq))
|
|
goto err_child;
|
|
/*
|
|
* If the sequence check on the child dentry passed, then
|
|
* the child has not been removed from its parent. This
|
|
* means the parent dentry must be valid and able to take
|
|
* a reference at this point.
|
|
*/
|
|
BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
|
|
BUG_ON(!parent->d_count);
|
|
parent->d_count++;
|
|
spin_unlock(&dentry->d_lock);
|
|
}
|
|
spin_unlock(&parent->d_lock);
|
|
if (want_root) {
|
|
path_get(&nd->root);
|
|
spin_unlock(&fs->lock);
|
|
}
|
|
mntget(nd->path.mnt);
|
|
|
|
rcu_read_unlock();
|
|
br_read_unlock(vfsmount_lock);
|
|
nd->flags &= ~LOOKUP_RCU;
|
|
return 0;
|
|
|
|
err_child:
|
|
spin_unlock(&dentry->d_lock);
|
|
err_parent:
|
|
spin_unlock(&parent->d_lock);
|
|
err_root:
|
|
if (want_root)
|
|
spin_unlock(&fs->lock);
|
|
return -ECHILD;
|
|
}
|
|
|
|
/**
|
|
* release_open_intent - free up open intent resources
|
|
* @nd: pointer to nameidata
|
|
*/
|
|
void release_open_intent(struct nameidata *nd)
|
|
{
|
|
struct file *file = nd->intent.open.file;
|
|
|
|
if (file && !IS_ERR(file)) {
|
|
if (file->f_path.dentry == NULL)
|
|
put_filp(file);
|
|
else
|
|
fput(file);
|
|
}
|
|
}
|
|
|
|
static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
|
|
{
|
|
return dentry->d_op->d_revalidate(dentry, nd);
|
|
}
|
|
|
|
/**
|
|
* complete_walk - successful completion of path walk
|
|
* @nd: pointer nameidata
|
|
*
|
|
* If we had been in RCU mode, drop out of it and legitimize nd->path.
|
|
* Revalidate the final result, unless we'd already done that during
|
|
* the path walk or the filesystem doesn't ask for it. Return 0 on
|
|
* success, -error on failure. In case of failure caller does not
|
|
* need to drop nd->path.
|
|
*/
|
|
static int complete_walk(struct nameidata *nd)
|
|
{
|
|
struct dentry *dentry = nd->path.dentry;
|
|
int status;
|
|
|
|
if (nd->flags & LOOKUP_RCU) {
|
|
nd->flags &= ~LOOKUP_RCU;
|
|
if (!(nd->flags & LOOKUP_ROOT))
|
|
nd->root.mnt = NULL;
|
|
spin_lock(&dentry->d_lock);
|
|
if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
|
|
spin_unlock(&dentry->d_lock);
|
|
rcu_read_unlock();
|
|
br_read_unlock(vfsmount_lock);
|
|
return -ECHILD;
|
|
}
|
|
BUG_ON(nd->inode != dentry->d_inode);
|
|
spin_unlock(&dentry->d_lock);
|
|
mntget(nd->path.mnt);
|
|
rcu_read_unlock();
|
|
br_read_unlock(vfsmount_lock);
|
|
}
|
|
|
|
if (likely(!(nd->flags & LOOKUP_JUMPED)))
|
|
return 0;
|
|
|
|
if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
|
|
return 0;
|
|
|
|
if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
|
|
return 0;
|
|
|
|
/* Note: we do not d_invalidate() */
|
|
status = d_revalidate(dentry, nd);
|
|
if (status > 0)
|
|
return 0;
|
|
|
|
if (!status)
|
|
status = -ESTALE;
|
|
|
|
path_put(&nd->path);
|
|
return status;
|
|
}
|
|
|
|
static __always_inline void set_root(struct nameidata *nd)
|
|
{
|
|
if (!nd->root.mnt)
|
|
get_fs_root(current->fs, &nd->root);
|
|
}
|
|
|
|
static int link_path_walk(const char *, struct nameidata *);
|
|
|
|
static __always_inline void set_root_rcu(struct nameidata *nd)
|
|
{
|
|
if (!nd->root.mnt) {
|
|
struct fs_struct *fs = current->fs;
|
|
unsigned seq;
|
|
|
|
do {
|
|
seq = read_seqcount_begin(&fs->seq);
|
|
nd->root = fs->root;
|
|
nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
|
|
} while (read_seqcount_retry(&fs->seq, seq));
|
|
}
|
|
}
|
|
|
|
static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
|
|
{
|
|
int ret;
|
|
|
|
if (IS_ERR(link))
|
|
goto fail;
|
|
|
|
if (*link == '/') {
|
|
set_root(nd);
|
|
path_put(&nd->path);
|
|
nd->path = nd->root;
|
|
path_get(&nd->root);
|
|
nd->flags |= LOOKUP_JUMPED;
|
|
}
|
|
nd->inode = nd->path.dentry->d_inode;
|
|
|
|
ret = link_path_walk(link, nd);
|
|
return ret;
|
|
fail:
|
|
path_put(&nd->path);
|
|
return PTR_ERR(link);
|
|
}
|
|
|
|
static void path_put_conditional(struct path *path, struct nameidata *nd)
|
|
{
|
|
dput(path->dentry);
|
|
if (path->mnt != nd->path.mnt)
|
|
mntput(path->mnt);
|
|
}
|
|
|
|
static inline void path_to_nameidata(const struct path *path,
|
|
struct nameidata *nd)
|
|
{
|
|
if (!(nd->flags & LOOKUP_RCU)) {
|
|
dput(nd->path.dentry);
|
|
if (nd->path.mnt != path->mnt)
|
|
mntput(nd->path.mnt);
|
|
}
|
|
nd->path.mnt = path->mnt;
|
|
nd->path.dentry = path->dentry;
|
|
}
|
|
|
|
static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
|
|
{
|
|
struct inode *inode = link->dentry->d_inode;
|
|
if (!IS_ERR(cookie) && inode->i_op->put_link)
|
|
inode->i_op->put_link(link->dentry, nd, cookie);
|
|
path_put(link);
|
|
}
|
|
|
|
static __always_inline int
|
|
follow_link(struct path *link, struct nameidata *nd, void **p)
|
|
{
|
|
int error;
|
|
struct dentry *dentry = link->dentry;
|
|
|
|
BUG_ON(nd->flags & LOOKUP_RCU);
|
|
|
|
if (link->mnt == nd->path.mnt)
|
|
mntget(link->mnt);
|
|
|
|
if (unlikely(current->total_link_count >= 40)) {
|
|
*p = ERR_PTR(-ELOOP); /* no ->put_link(), please */
|
|
path_put(&nd->path);
|
|
return -ELOOP;
|
|
}
|
|
cond_resched();
|
|
current->total_link_count++;
|
|
|
|
touch_atime(link);
|
|
nd_set_link(nd, NULL);
|
|
|
|
error = security_inode_follow_link(link->dentry, nd);
|
|
if (error) {
|
|
*p = ERR_PTR(error); /* no ->put_link(), please */
|
|
path_put(&nd->path);
|
|
return error;
|
|
}
|
|
|
|
nd->last_type = LAST_BIND;
|
|
*p = dentry->d_inode->i_op->follow_link(dentry, nd);
|
|
error = PTR_ERR(*p);
|
|
if (!IS_ERR(*p)) {
|
|
char *s = nd_get_link(nd);
|
|
error = 0;
|
|
if (s)
|
|
error = __vfs_follow_link(nd, s);
|
|
else if (nd->last_type == LAST_BIND) {
|
|
nd->flags |= LOOKUP_JUMPED;
|
|
nd->inode = nd->path.dentry->d_inode;
|
|
if (nd->inode->i_op->follow_link) {
|
|
/* stepped on a _really_ weird one */
|
|
path_put(&nd->path);
|
|
error = -ELOOP;
|
|
}
|
|
}
|
|
}
|
|
return error;
|
|
}
|
|
|
|
static int follow_up_rcu(struct path *path)
|
|
{
|
|
struct mount *mnt = real_mount(path->mnt);
|
|
struct mount *parent;
|
|
struct dentry *mountpoint;
|
|
|
|
parent = mnt->mnt_parent;
|
|
if (&parent->mnt == path->mnt)
|
|
return 0;
|
|
mountpoint = mnt->mnt_mountpoint;
|
|
path->dentry = mountpoint;
|
|
path->mnt = &parent->mnt;
|
|
return 1;
|
|
}
|
|
|
|
int follow_up(struct path *path)
|
|
{
|
|
struct mount *mnt = real_mount(path->mnt);
|
|
struct mount *parent;
|
|
struct dentry *mountpoint;
|
|
|
|
br_read_lock(vfsmount_lock);
|
|
parent = mnt->mnt_parent;
|
|
if (&parent->mnt == path->mnt) {
|
|
br_read_unlock(vfsmount_lock);
|
|
return 0;
|
|
}
|
|
mntget(&parent->mnt);
|
|
mountpoint = dget(mnt->mnt_mountpoint);
|
|
br_read_unlock(vfsmount_lock);
|
|
dput(path->dentry);
|
|
path->dentry = mountpoint;
|
|
mntput(path->mnt);
|
|
path->mnt = &parent->mnt;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Perform an automount
|
|
* - return -EISDIR to tell follow_managed() to stop and return the path we
|
|
* were called with.
|
|
*/
|
|
static int follow_automount(struct path *path, unsigned flags,
|
|
bool *need_mntput)
|
|
{
|
|
struct vfsmount *mnt;
|
|
int err;
|
|
|
|
if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
|
|
return -EREMOTE;
|
|
|
|
/* We don't want to mount if someone's just doing a stat -
|
|
* unless they're stat'ing a directory and appended a '/' to
|
|
* the name.
|
|
*
|
|
* We do, however, want to mount if someone wants to open or
|
|
* create a file of any type under the mountpoint, wants to
|
|
* traverse through the mountpoint or wants to open the
|
|
* mounted directory. Also, autofs may mark negative dentries
|
|
* as being automount points. These will need the attentions
|
|
* of the daemon to instantiate them before they can be used.
|
|
*/
|
|
if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
|
|
LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
|
|
path->dentry->d_inode)
|
|
return -EISDIR;
|
|
|
|
current->total_link_count++;
|
|
if (current->total_link_count >= 40)
|
|
return -ELOOP;
|
|
|
|
mnt = path->dentry->d_op->d_automount(path);
|
|
if (IS_ERR(mnt)) {
|
|
/*
|
|
* The filesystem is allowed to return -EISDIR here to indicate
|
|
* it doesn't want to automount. For instance, autofs would do
|
|
* this so that its userspace daemon can mount on this dentry.
|
|
*
|
|
* However, we can only permit this if it's a terminal point in
|
|
* the path being looked up; if it wasn't then the remainder of
|
|
* the path is inaccessible and we should say so.
|
|
*/
|
|
if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
|
|
return -EREMOTE;
|
|
return PTR_ERR(mnt);
|
|
}
|
|
|
|
if (!mnt) /* mount collision */
|
|
return 0;
|
|
|
|
if (!*need_mntput) {
|
|
/* lock_mount() may release path->mnt on error */
|
|
mntget(path->mnt);
|
|
*need_mntput = true;
|
|
}
|
|
err = finish_automount(mnt, path);
|
|
|
|
switch (err) {
|
|
case -EBUSY:
|
|
/* Someone else made a mount here whilst we were busy */
|
|
return 0;
|
|
case 0:
|
|
path_put(path);
|
|
path->mnt = mnt;
|
|
path->dentry = dget(mnt->mnt_root);
|
|
return 0;
|
|
default:
|
|
return err;
|
|
}
|
|
|
|
}
|
|
|
|
/*
|
|
* Handle a dentry that is managed in some way.
|
|
* - Flagged for transit management (autofs)
|
|
* - Flagged as mountpoint
|
|
* - Flagged as automount point
|
|
*
|
|
* This may only be called in refwalk mode.
|
|
*
|
|
* Serialization is taken care of in namespace.c
|
|
*/
|
|
static int follow_managed(struct path *path, unsigned flags)
|
|
{
|
|
struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
|
|
unsigned managed;
|
|
bool need_mntput = false;
|
|
int ret = 0;
|
|
|
|
/* Given that we're not holding a lock here, we retain the value in a
|
|
* local variable for each dentry as we look at it so that we don't see
|
|
* the components of that value change under us */
|
|
while (managed = ACCESS_ONCE(path->dentry->d_flags),
|
|
managed &= DCACHE_MANAGED_DENTRY,
|
|
unlikely(managed != 0)) {
|
|
/* Allow the filesystem to manage the transit without i_mutex
|
|
* being held. */
|
|
if (managed & DCACHE_MANAGE_TRANSIT) {
|
|
BUG_ON(!path->dentry->d_op);
|
|
BUG_ON(!path->dentry->d_op->d_manage);
|
|
ret = path->dentry->d_op->d_manage(path->dentry, false);
|
|
if (ret < 0)
|
|
break;
|
|
}
|
|
|
|
/* Transit to a mounted filesystem. */
|
|
if (managed & DCACHE_MOUNTED) {
|
|
struct vfsmount *mounted = lookup_mnt(path);
|
|
if (mounted) {
|
|
dput(path->dentry);
|
|
if (need_mntput)
|
|
mntput(path->mnt);
|
|
path->mnt = mounted;
|
|
path->dentry = dget(mounted->mnt_root);
|
|
need_mntput = true;
|
|
continue;
|
|
}
|
|
|
|
/* Something is mounted on this dentry in another
|
|
* namespace and/or whatever was mounted there in this
|
|
* namespace got unmounted before we managed to get the
|
|
* vfsmount_lock */
|
|
}
|
|
|
|
/* Handle an automount point */
|
|
if (managed & DCACHE_NEED_AUTOMOUNT) {
|
|
ret = follow_automount(path, flags, &need_mntput);
|
|
if (ret < 0)
|
|
break;
|
|
continue;
|
|
}
|
|
|
|
/* We didn't change the current path point */
|
|
break;
|
|
}
|
|
|
|
if (need_mntput && path->mnt == mnt)
|
|
mntput(path->mnt);
|
|
if (ret == -EISDIR)
|
|
ret = 0;
|
|
return ret < 0 ? ret : need_mntput;
|
|
}
|
|
|
|
int follow_down_one(struct path *path)
|
|
{
|
|
struct vfsmount *mounted;
|
|
|
|
mounted = lookup_mnt(path);
|
|
if (mounted) {
|
|
dput(path->dentry);
|
|
mntput(path->mnt);
|
|
path->mnt = mounted;
|
|
path->dentry = dget(mounted->mnt_root);
|
|
return 1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static inline bool managed_dentry_might_block(struct dentry *dentry)
|
|
{
|
|
return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
|
|
dentry->d_op->d_manage(dentry, true) < 0);
|
|
}
|
|
|
|
/*
|
|
* Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
|
|
* we meet a managed dentry that would need blocking.
|
|
*/
|
|
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
|
|
struct inode **inode)
|
|
{
|
|
for (;;) {
|
|
struct mount *mounted;
|
|
/*
|
|
* Don't forget we might have a non-mountpoint managed dentry
|
|
* that wants to block transit.
|
|
*/
|
|
if (unlikely(managed_dentry_might_block(path->dentry)))
|
|
return false;
|
|
|
|
if (!d_mountpoint(path->dentry))
|
|
break;
|
|
|
|
mounted = __lookup_mnt(path->mnt, path->dentry, 1);
|
|
if (!mounted)
|
|
break;
|
|
path->mnt = &mounted->mnt;
|
|
path->dentry = mounted->mnt.mnt_root;
|
|
nd->flags |= LOOKUP_JUMPED;
|
|
nd->seq = read_seqcount_begin(&path->dentry->d_seq);
|
|
/*
|
|
* Update the inode too. We don't need to re-check the
|
|
* dentry sequence number here after this d_inode read,
|
|
* because a mount-point is always pinned.
|
|
*/
|
|
*inode = path->dentry->d_inode;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static void follow_mount_rcu(struct nameidata *nd)
|
|
{
|
|
while (d_mountpoint(nd->path.dentry)) {
|
|
struct mount *mounted;
|
|
mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
|
|
if (!mounted)
|
|
break;
|
|
nd->path.mnt = &mounted->mnt;
|
|
nd->path.dentry = mounted->mnt.mnt_root;
|
|
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
|
|
}
|
|
}
|
|
|
|
static int follow_dotdot_rcu(struct nameidata *nd)
|
|
{
|
|
set_root_rcu(nd);
|
|
|
|
while (1) {
|
|
if (nd->path.dentry == nd->root.dentry &&
|
|
nd->path.mnt == nd->root.mnt) {
|
|
break;
|
|
}
|
|
if (nd->path.dentry != nd->path.mnt->mnt_root) {
|
|
struct dentry *old = nd->path.dentry;
|
|
struct dentry *parent = old->d_parent;
|
|
unsigned seq;
|
|
|
|
seq = read_seqcount_begin(&parent->d_seq);
|
|
if (read_seqcount_retry(&old->d_seq, nd->seq))
|
|
goto failed;
|
|
nd->path.dentry = parent;
|
|
nd->seq = seq;
|
|
break;
|
|
}
|
|
if (!follow_up_rcu(&nd->path))
|
|
break;
|
|
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
|
|
}
|
|
follow_mount_rcu(nd);
|
|
nd->inode = nd->path.dentry->d_inode;
|
|
return 0;
|
|
|
|
failed:
|
|
nd->flags &= ~LOOKUP_RCU;
|
|
if (!(nd->flags & LOOKUP_ROOT))
|
|
nd->root.mnt = NULL;
|
|
rcu_read_unlock();
|
|
br_read_unlock(vfsmount_lock);
|
|
return -ECHILD;
|
|
}
|
|
|
|
/*
|
|
* Follow down to the covering mount currently visible to userspace. At each
|
|
* point, the filesystem owning that dentry may be queried as to whether the
|
|
* caller is permitted to proceed or not.
|
|
*/
|
|
int follow_down(struct path *path)
|
|
{
|
|
unsigned managed;
|
|
int ret;
|
|
|
|
while (managed = ACCESS_ONCE(path->dentry->d_flags),
|
|
unlikely(managed & DCACHE_MANAGED_DENTRY)) {
|
|
/* Allow the filesystem to manage the transit without i_mutex
|
|
* being held.
|
|
*
|
|
* We indicate to the filesystem if someone is trying to mount
|
|
* something here. This gives autofs the chance to deny anyone
|
|
* other than its daemon the right to mount on its
|
|
* superstructure.
|
|
*
|
|
* The filesystem may sleep at this point.
|
|
*/
|
|
if (managed & DCACHE_MANAGE_TRANSIT) {
|
|
BUG_ON(!path->dentry->d_op);
|
|
BUG_ON(!path->dentry->d_op->d_manage);
|
|
ret = path->dentry->d_op->d_manage(
|
|
path->dentry, false);
|
|
if (ret < 0)
|
|
return ret == -EISDIR ? 0 : ret;
|
|
}
|
|
|
|
/* Transit to a mounted filesystem. */
|
|
if (managed & DCACHE_MOUNTED) {
|
|
struct vfsmount *mounted = lookup_mnt(path);
|
|
if (!mounted)
|
|
break;
|
|
dput(path->dentry);
|
|
mntput(path->mnt);
|
|
path->mnt = mounted;
|
|
path->dentry = dget(mounted->mnt_root);
|
|
continue;
|
|
}
|
|
|
|
/* Don't handle automount points here */
|
|
break;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
|
|
*/
|
|
static void follow_mount(struct path *path)
|
|
{
|
|
while (d_mountpoint(path->dentry)) {
|
|
struct vfsmount *mounted = lookup_mnt(path);
|
|
if (!mounted)
|
|
break;
|
|
dput(path->dentry);
|
|
mntput(path->mnt);
|
|
path->mnt = mounted;
|
|
path->dentry = dget(mounted->mnt_root);
|
|
}
|
|
}
|
|
|
|
static void follow_dotdot(struct nameidata *nd)
|
|
{
|
|
set_root(nd);
|
|
|
|
while(1) {
|
|
struct dentry *old = nd->path.dentry;
|
|
|
|
if (nd->path.dentry == nd->root.dentry &&
|
|
nd->path.mnt == nd->root.mnt) {
|
|
break;
|
|
}
|
|
if (nd->path.dentry != nd->path.mnt->mnt_root) {
|
|
/* rare case of legitimate dget_parent()... */
|
|
nd->path.dentry = dget_parent(nd->path.dentry);
|
|
dput(old);
|
|
break;
|
|
}
|
|
if (!follow_up(&nd->path))
|
|
break;
|
|
}
|
|
follow_mount(&nd->path);
|
|
nd->inode = nd->path.dentry->d_inode;
|
|
}
|
|
|
|
/*
|
|
* This looks up the name in dcache, possibly revalidates the old dentry and
|
|
* allocates a new one if not found or not valid. In the need_lookup argument
|
|
* returns whether i_op->lookup is necessary.
|
|
*
|
|
* dir->d_inode->i_mutex must be held
|
|
*/
|
|
static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
|
|
struct nameidata *nd, bool *need_lookup)
|
|
{
|
|
struct dentry *dentry;
|
|
int error;
|
|
|
|
*need_lookup = false;
|
|
dentry = d_lookup(dir, name);
|
|
if (dentry) {
|
|
if (d_need_lookup(dentry)) {
|
|
*need_lookup = true;
|
|
} else if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
|
|
error = d_revalidate(dentry, nd);
|
|
if (unlikely(error <= 0)) {
|
|
if (error < 0) {
|
|
dput(dentry);
|
|
return ERR_PTR(error);
|
|
} else if (!d_invalidate(dentry)) {
|
|
dput(dentry);
|
|
dentry = NULL;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!dentry) {
|
|
dentry = d_alloc(dir, name);
|
|
if (unlikely(!dentry))
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
*need_lookup = true;
|
|
}
|
|
return dentry;
|
|
}
|
|
|
|
/*
|
|
* Call i_op->lookup on the dentry. The dentry must be negative but may be
|
|
* hashed if it was pouplated with DCACHE_NEED_LOOKUP.
|
|
*
|
|
* dir->d_inode->i_mutex must be held
|
|
*/
|
|
static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
|
|
struct nameidata *nd)
|
|
{
|
|
struct dentry *old;
|
|
|
|
/* Don't create child dentry for a dead directory. */
|
|
if (unlikely(IS_DEADDIR(dir))) {
|
|
dput(dentry);
|
|
return ERR_PTR(-ENOENT);
|
|
}
|
|
|
|
old = dir->i_op->lookup(dir, dentry, nd);
|
|
if (unlikely(old)) {
|
|
dput(dentry);
|
|
dentry = old;
|
|
}
|
|
return dentry;
|
|
}
|
|
|
|
static struct dentry *__lookup_hash(struct qstr *name,
|
|
struct dentry *base, struct nameidata *nd)
|
|
{
|
|
bool need_lookup;
|
|
struct dentry *dentry;
|
|
|
|
dentry = lookup_dcache(name, base, nd, &need_lookup);
|
|
if (!need_lookup)
|
|
return dentry;
|
|
|
|
return lookup_real(base->d_inode, dentry, nd);
|
|
}
|
|
|
|
/*
|
|
* It's more convoluted than I'd like it to be, but... it's still fairly
|
|
* small and for now I'd prefer to have fast path as straight as possible.
|
|
* It _is_ time-critical.
|
|
*/
|
|
static int do_lookup(struct nameidata *nd, struct qstr *name,
|
|
struct path *path, struct inode **inode)
|
|
{
|
|
struct vfsmount *mnt = nd->path.mnt;
|
|
struct dentry *dentry, *parent = nd->path.dentry;
|
|
int need_reval = 1;
|
|
int status = 1;
|
|
int err;
|
|
|
|
/*
|
|
* Rename seqlock is not required here because in the off chance
|
|
* of a false negative due to a concurrent rename, we're going to
|
|
* do the non-racy lookup, below.
|
|
*/
|
|
if (nd->flags & LOOKUP_RCU) {
|
|
unsigned seq;
|
|
*inode = nd->inode;
|
|
dentry = __d_lookup_rcu(parent, name, &seq, inode);
|
|
if (!dentry)
|
|
goto unlazy;
|
|
|
|
/* Memory barrier in read_seqcount_begin of child is enough */
|
|
if (__read_seqcount_retry(&parent->d_seq, nd->seq))
|
|
return -ECHILD;
|
|
nd->seq = seq;
|
|
|
|
if (unlikely(d_need_lookup(dentry)))
|
|
goto unlazy;
|
|
if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
|
|
status = d_revalidate(dentry, nd);
|
|
if (unlikely(status <= 0)) {
|
|
if (status != -ECHILD)
|
|
need_reval = 0;
|
|
goto unlazy;
|
|
}
|
|
}
|
|
path->mnt = mnt;
|
|
path->dentry = dentry;
|
|
if (unlikely(!__follow_mount_rcu(nd, path, inode)))
|
|
goto unlazy;
|
|
if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
|
|
goto unlazy;
|
|
return 0;
|
|
unlazy:
|
|
if (unlazy_walk(nd, dentry))
|
|
return -ECHILD;
|
|
} else {
|
|
dentry = __d_lookup(parent, name);
|
|
}
|
|
|
|
if (unlikely(!dentry))
|
|
goto need_lookup;
|
|
|
|
if (unlikely(d_need_lookup(dentry))) {
|
|
dput(dentry);
|
|
goto need_lookup;
|
|
}
|
|
|
|
if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
|
|
status = d_revalidate(dentry, nd);
|
|
if (unlikely(status <= 0)) {
|
|
if (status < 0) {
|
|
dput(dentry);
|
|
return status;
|
|
}
|
|
if (!d_invalidate(dentry)) {
|
|
dput(dentry);
|
|
goto need_lookup;
|
|
}
|
|
}
|
|
done:
|
|
path->mnt = mnt;
|
|
path->dentry = dentry;
|
|
err = follow_managed(path, nd->flags);
|
|
if (unlikely(err < 0)) {
|
|
path_put_conditional(path, nd);
|
|
return err;
|
|
}
|
|
if (err)
|
|
nd->flags |= LOOKUP_JUMPED;
|
|
*inode = path->dentry->d_inode;
|
|
return 0;
|
|
|
|
need_lookup:
|
|
BUG_ON(nd->inode != parent->d_inode);
|
|
|
|
mutex_lock(&parent->d_inode->i_mutex);
|
|
dentry = __lookup_hash(name, parent, nd);
|
|
mutex_unlock(&parent->d_inode->i_mutex);
|
|
if (IS_ERR(dentry))
|
|
return PTR_ERR(dentry);
|
|
goto done;
|
|
}
|
|
|
|
static inline int may_lookup(struct nameidata *nd)
|
|
{
|
|
if (nd->flags & LOOKUP_RCU) {
|
|
int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
|
|
if (err != -ECHILD)
|
|
return err;
|
|
if (unlazy_walk(nd, NULL))
|
|
return -ECHILD;
|
|
}
|
|
return inode_permission(nd->inode, MAY_EXEC);
|
|
}
|
|
|
|
static inline int handle_dots(struct nameidata *nd, int type)
|
|
{
|
|
if (type == LAST_DOTDOT) {
|
|
if (nd->flags & LOOKUP_RCU) {
|
|
if (follow_dotdot_rcu(nd))
|
|
return -ECHILD;
|
|
} else
|
|
follow_dotdot(nd);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void terminate_walk(struct nameidata *nd)
|
|
{
|
|
if (!(nd->flags & LOOKUP_RCU)) {
|
|
path_put(&nd->path);
|
|
} else {
|
|
nd->flags &= ~LOOKUP_RCU;
|
|
if (!(nd->flags & LOOKUP_ROOT))
|
|
nd->root.mnt = NULL;
|
|
rcu_read_unlock();
|
|
br_read_unlock(vfsmount_lock);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Do we need to follow links? We _really_ want to be able
|
|
* to do this check without having to look at inode->i_op,
|
|
* so we keep a cache of "no, this doesn't need follow_link"
|
|
* for the common case.
|
|
*/
|
|
static inline int should_follow_link(struct inode *inode, int follow)
|
|
{
|
|
if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
|
|
if (likely(inode->i_op->follow_link))
|
|
return follow;
|
|
|
|
/* This gets set once for the inode lifetime */
|
|
spin_lock(&inode->i_lock);
|
|
inode->i_opflags |= IOP_NOFOLLOW;
|
|
spin_unlock(&inode->i_lock);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static inline int walk_component(struct nameidata *nd, struct path *path,
|
|
struct qstr *name, int type, int follow)
|
|
{
|
|
struct inode *inode;
|
|
int err;
|
|
/*
|
|
* "." and ".." are special - ".." especially so because it has
|
|
* to be able to know about the current root directory and
|
|
* parent relationships.
|
|
*/
|
|
if (unlikely(type != LAST_NORM))
|
|
return handle_dots(nd, type);
|
|
err = do_lookup(nd, name, path, &inode);
|
|
if (unlikely(err)) {
|
|
terminate_walk(nd);
|
|
return err;
|
|
}
|
|
if (!inode) {
|
|
path_to_nameidata(path, nd);
|
|
terminate_walk(nd);
|
|
return -ENOENT;
|
|
}
|
|
if (should_follow_link(inode, follow)) {
|
|
if (nd->flags & LOOKUP_RCU) {
|
|
if (unlikely(unlazy_walk(nd, path->dentry))) {
|
|
terminate_walk(nd);
|
|
return -ECHILD;
|
|
}
|
|
}
|
|
BUG_ON(inode != path->dentry->d_inode);
|
|
return 1;
|
|
}
|
|
path_to_nameidata(path, nd);
|
|
nd->inode = inode;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* This limits recursive symlink follows to 8, while
|
|
* limiting consecutive symlinks to 40.
|
|
*
|
|
* Without that kind of total limit, nasty chains of consecutive
|
|
* symlinks can cause almost arbitrarily long lookups.
|
|
*/
|
|
static inline int nested_symlink(struct path *path, struct nameidata *nd)
|
|
{
|
|
int res;
|
|
|
|
if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
|
|
path_put_conditional(path, nd);
|
|
path_put(&nd->path);
|
|
return -ELOOP;
|
|
}
|
|
BUG_ON(nd->depth >= MAX_NESTED_LINKS);
|
|
|
|
nd->depth++;
|
|
current->link_count++;
|
|
|
|
do {
|
|
struct path link = *path;
|
|
void *cookie;
|
|
|
|
res = follow_link(&link, nd, &cookie);
|
|
if (!res)
|
|
res = walk_component(nd, path, &nd->last,
|
|
nd->last_type, LOOKUP_FOLLOW);
|
|
put_link(nd, &link, cookie);
|
|
} while (res > 0);
|
|
|
|
current->link_count--;
|
|
nd->depth--;
|
|
return res;
|
|
}
|
|
|
|
/*
|
|
* We really don't want to look at inode->i_op->lookup
|
|
* when we don't have to. So we keep a cache bit in
|
|
* the inode ->i_opflags field that says "yes, we can
|
|
* do lookup on this inode".
|
|
*/
|
|
static inline int can_lookup(struct inode *inode)
|
|
{
|
|
if (likely(inode->i_opflags & IOP_LOOKUP))
|
|
return 1;
|
|
if (likely(!inode->i_op->lookup))
|
|
return 0;
|
|
|
|
/* We do this once for the lifetime of the inode */
|
|
spin_lock(&inode->i_lock);
|
|
inode->i_opflags |= IOP_LOOKUP;
|
|
spin_unlock(&inode->i_lock);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* We can do the critical dentry name comparison and hashing
|
|
* operations one word at a time, but we are limited to:
|
|
*
|
|
* - Architectures with fast unaligned word accesses. We could
|
|
* do a "get_unaligned()" if this helps and is sufficiently
|
|
* fast.
|
|
*
|
|
* - Little-endian machines (so that we can generate the mask
|
|
* of low bytes efficiently). Again, we *could* do a byte
|
|
* swapping load on big-endian architectures if that is not
|
|
* expensive enough to make the optimization worthless.
|
|
*
|
|
* - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
|
|
* do not trap on the (extremely unlikely) case of a page
|
|
* crossing operation.
|
|
*
|
|
* - Furthermore, we need an efficient 64-bit compile for the
|
|
* 64-bit case in order to generate the "number of bytes in
|
|
* the final mask". Again, that could be replaced with a
|
|
* efficient population count instruction or similar.
|
|
*/
|
|
#ifdef CONFIG_DCACHE_WORD_ACCESS
|
|
|
|
#include <asm/word-at-a-time.h>
|
|
|
|
#ifdef CONFIG_64BIT
|
|
|
|
static inline unsigned int fold_hash(unsigned long hash)
|
|
{
|
|
hash += hash >> (8*sizeof(int));
|
|
return hash;
|
|
}
|
|
|
|
#else /* 32-bit case */
|
|
|
|
#define fold_hash(x) (x)
|
|
|
|
#endif
|
|
|
|
unsigned int full_name_hash(const unsigned char *name, unsigned int len)
|
|
{
|
|
unsigned long a, mask;
|
|
unsigned long hash = 0;
|
|
|
|
for (;;) {
|
|
a = *(unsigned long *)name;
|
|
if (len < sizeof(unsigned long))
|
|
break;
|
|
hash += a;
|
|
hash *= 9;
|
|
name += sizeof(unsigned long);
|
|
len -= sizeof(unsigned long);
|
|
if (!len)
|
|
goto done;
|
|
}
|
|
mask = ~(~0ul << len*8);
|
|
hash += mask & a;
|
|
done:
|
|
return fold_hash(hash);
|
|
}
|
|
EXPORT_SYMBOL(full_name_hash);
|
|
|
|
/*
|
|
* Calculate the length and hash of the path component, and
|
|
* return the length of the component;
|
|
*/
|
|
static inline unsigned long hash_name(const char *name, unsigned int *hashp)
|
|
{
|
|
unsigned long a, mask, hash, len;
|
|
|
|
hash = a = 0;
|
|
len = -sizeof(unsigned long);
|
|
do {
|
|
hash = (hash + a) * 9;
|
|
len += sizeof(unsigned long);
|
|
a = *(unsigned long *)(name+len);
|
|
/* Do we have any NUL or '/' bytes in this word? */
|
|
mask = has_zero(a) | has_zero(a ^ REPEAT_BYTE('/'));
|
|
} while (!mask);
|
|
|
|
/* The mask *below* the first high bit set */
|
|
mask = (mask - 1) & ~mask;
|
|
mask >>= 7;
|
|
hash += a & mask;
|
|
*hashp = fold_hash(hash);
|
|
|
|
return len + count_masked_bytes(mask);
|
|
}
|
|
|
|
#else
|
|
|
|
unsigned int full_name_hash(const unsigned char *name, unsigned int len)
|
|
{
|
|
unsigned long hash = init_name_hash();
|
|
while (len--)
|
|
hash = partial_name_hash(*name++, hash);
|
|
return end_name_hash(hash);
|
|
}
|
|
EXPORT_SYMBOL(full_name_hash);
|
|
|
|
/*
|
|
* We know there's a real path component here of at least
|
|
* one character.
|
|
*/
|
|
static inline unsigned long hash_name(const char *name, unsigned int *hashp)
|
|
{
|
|
unsigned long hash = init_name_hash();
|
|
unsigned long len = 0, c;
|
|
|
|
c = (unsigned char)*name;
|
|
do {
|
|
len++;
|
|
hash = partial_name_hash(c, hash);
|
|
c = (unsigned char)name[len];
|
|
} while (c && c != '/');
|
|
*hashp = end_name_hash(hash);
|
|
return len;
|
|
}
|
|
|
|
#endif
|
|
|
|
/*
|
|
* Name resolution.
|
|
* This is the basic name resolution function, turning a pathname into
|
|
* the final dentry. We expect 'base' to be positive and a directory.
|
|
*
|
|
* Returns 0 and nd will have valid dentry and mnt on success.
|
|
* Returns error and drops reference to input namei data on failure.
|
|
*/
|
|
static int link_path_walk(const char *name, struct nameidata *nd)
|
|
{
|
|
struct path next;
|
|
int err;
|
|
|
|
while (*name=='/')
|
|
name++;
|
|
if (!*name)
|
|
return 0;
|
|
|
|
/* At this point we know we have a real path component. */
|
|
for(;;) {
|
|
struct qstr this;
|
|
long len;
|
|
int type;
|
|
|
|
err = may_lookup(nd);
|
|
if (err)
|
|
break;
|
|
|
|
len = hash_name(name, &this.hash);
|
|
this.name = name;
|
|
this.len = len;
|
|
|
|
type = LAST_NORM;
|
|
if (name[0] == '.') switch (len) {
|
|
case 2:
|
|
if (name[1] == '.') {
|
|
type = LAST_DOTDOT;
|
|
nd->flags |= LOOKUP_JUMPED;
|
|
}
|
|
break;
|
|
case 1:
|
|
type = LAST_DOT;
|
|
}
|
|
if (likely(type == LAST_NORM)) {
|
|
struct dentry *parent = nd->path.dentry;
|
|
nd->flags &= ~LOOKUP_JUMPED;
|
|
if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
|
|
err = parent->d_op->d_hash(parent, nd->inode,
|
|
&this);
|
|
if (err < 0)
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (!name[len])
|
|
goto last_component;
|
|
/*
|
|
* If it wasn't NUL, we know it was '/'. Skip that
|
|
* slash, and continue until no more slashes.
|
|
*/
|
|
do {
|
|
len++;
|
|
} while (unlikely(name[len] == '/'));
|
|
if (!name[len])
|
|
goto last_component;
|
|
name += len;
|
|
|
|
err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
|
|
if (err < 0)
|
|
return err;
|
|
|
|
if (err) {
|
|
err = nested_symlink(&next, nd);
|
|
if (err)
|
|
return err;
|
|
}
|
|
if (can_lookup(nd->inode))
|
|
continue;
|
|
err = -ENOTDIR;
|
|
break;
|
|
/* here ends the main loop */
|
|
|
|
last_component:
|
|
nd->last = this;
|
|
nd->last_type = type;
|
|
return 0;
|
|
}
|
|
terminate_walk(nd);
|
|
return err;
|
|
}
|
|
|
|
static int path_init(int dfd, const char *name, unsigned int flags,
|
|
struct nameidata *nd, struct file **fp)
|
|
{
|
|
int retval = 0;
|
|
int fput_needed;
|
|
struct file *file;
|
|
|
|
nd->last_type = LAST_ROOT; /* if there are only slashes... */
|
|
nd->flags = flags | LOOKUP_JUMPED;
|
|
nd->depth = 0;
|
|
if (flags & LOOKUP_ROOT) {
|
|
struct inode *inode = nd->root.dentry->d_inode;
|
|
if (*name) {
|
|
if (!inode->i_op->lookup)
|
|
return -ENOTDIR;
|
|
retval = inode_permission(inode, MAY_EXEC);
|
|
if (retval)
|
|
return retval;
|
|
}
|
|
nd->path = nd->root;
|
|
nd->inode = inode;
|
|
if (flags & LOOKUP_RCU) {
|
|
br_read_lock(vfsmount_lock);
|
|
rcu_read_lock();
|
|
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
|
|
} else {
|
|
path_get(&nd->path);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
nd->root.mnt = NULL;
|
|
|
|
if (*name=='/') {
|
|
if (flags & LOOKUP_RCU) {
|
|
br_read_lock(vfsmount_lock);
|
|
rcu_read_lock();
|
|
set_root_rcu(nd);
|
|
} else {
|
|
set_root(nd);
|
|
path_get(&nd->root);
|
|
}
|
|
nd->path = nd->root;
|
|
} else if (dfd == AT_FDCWD) {
|
|
if (flags & LOOKUP_RCU) {
|
|
struct fs_struct *fs = current->fs;
|
|
unsigned seq;
|
|
|
|
br_read_lock(vfsmount_lock);
|
|
rcu_read_lock();
|
|
|
|
do {
|
|
seq = read_seqcount_begin(&fs->seq);
|
|
nd->path = fs->pwd;
|
|
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
|
|
} while (read_seqcount_retry(&fs->seq, seq));
|
|
} else {
|
|
get_fs_pwd(current->fs, &nd->path);
|
|
}
|
|
} else {
|
|
struct dentry *dentry;
|
|
|
|
file = fget_raw_light(dfd, &fput_needed);
|
|
retval = -EBADF;
|
|
if (!file)
|
|
goto out_fail;
|
|
|
|
dentry = file->f_path.dentry;
|
|
|
|
if (*name) {
|
|
retval = -ENOTDIR;
|
|
if (!S_ISDIR(dentry->d_inode->i_mode))
|
|
goto fput_fail;
|
|
|
|
retval = inode_permission(dentry->d_inode, MAY_EXEC);
|
|
if (retval)
|
|
goto fput_fail;
|
|
}
|
|
|
|
nd->path = file->f_path;
|
|
if (flags & LOOKUP_RCU) {
|
|
if (fput_needed)
|
|
*fp = file;
|
|
nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
|
|
br_read_lock(vfsmount_lock);
|
|
rcu_read_lock();
|
|
} else {
|
|
path_get(&file->f_path);
|
|
fput_light(file, fput_needed);
|
|
}
|
|
}
|
|
|
|
nd->inode = nd->path.dentry->d_inode;
|
|
return 0;
|
|
|
|
fput_fail:
|
|
fput_light(file, fput_needed);
|
|
out_fail:
|
|
return retval;
|
|
}
|
|
|
|
static inline int lookup_last(struct nameidata *nd, struct path *path)
|
|
{
|
|
if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
|
|
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
|
|
|
|
nd->flags &= ~LOOKUP_PARENT;
|
|
return walk_component(nd, path, &nd->last, nd->last_type,
|
|
nd->flags & LOOKUP_FOLLOW);
|
|
}
|
|
|
|
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
|
|
static int path_lookupat(int dfd, const char *name,
|
|
unsigned int flags, struct nameidata *nd)
|
|
{
|
|
struct file *base = NULL;
|
|
struct path path;
|
|
int err;
|
|
|
|
/*
|
|
* Path walking is largely split up into 2 different synchronisation
|
|
* schemes, rcu-walk and ref-walk (explained in
|
|
* Documentation/filesystems/path-lookup.txt). These share much of the
|
|
* path walk code, but some things particularly setup, cleanup, and
|
|
* following mounts are sufficiently divergent that functions are
|
|
* duplicated. Typically there is a function foo(), and its RCU
|
|
* analogue, foo_rcu().
|
|
*
|
|
* -ECHILD is the error number of choice (just to avoid clashes) that
|
|
* is returned if some aspect of an rcu-walk fails. Such an error must
|
|
* be handled by restarting a traditional ref-walk (which will always
|
|
* be able to complete).
|
|
*/
|
|
err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
|
|
|
|
if (unlikely(err))
|
|
return err;
|
|
|
|
current->total_link_count = 0;
|
|
err = link_path_walk(name, nd);
|
|
|
|
if (!err && !(flags & LOOKUP_PARENT)) {
|
|
err = lookup_last(nd, &path);
|
|
while (err > 0) {
|
|
void *cookie;
|
|
struct path link = path;
|
|
nd->flags |= LOOKUP_PARENT;
|
|
err = follow_link(&link, nd, &cookie);
|
|
if (!err)
|
|
err = lookup_last(nd, &path);
|
|
put_link(nd, &link, cookie);
|
|
}
|
|
}
|
|
|
|
if (!err)
|
|
err = complete_walk(nd);
|
|
|
|
if (!err && nd->flags & LOOKUP_DIRECTORY) {
|
|
if (!nd->inode->i_op->lookup) {
|
|
path_put(&nd->path);
|
|
err = -ENOTDIR;
|
|
}
|
|
}
|
|
|
|
if (base)
|
|
fput(base);
|
|
|
|
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
|
|
path_put(&nd->root);
|
|
nd->root.mnt = NULL;
|
|
}
|
|
return err;
|
|
}
|
|
|
|
static int do_path_lookup(int dfd, const char *name,
|
|
unsigned int flags, struct nameidata *nd)
|
|
{
|
|
int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
|
|
if (unlikely(retval == -ECHILD))
|
|
retval = path_lookupat(dfd, name, flags, nd);
|
|
if (unlikely(retval == -ESTALE))
|
|
retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);
|
|
|
|
if (likely(!retval)) {
|
|
if (unlikely(!audit_dummy_context())) {
|
|
if (nd->path.dentry && nd->inode)
|
|
audit_inode(name, nd->path.dentry);
|
|
}
|
|
}
|
|
return retval;
|
|
}
|
|
|
|
int kern_path_parent(const char *name, struct nameidata *nd)
|
|
{
|
|
return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd);
|
|
}
|
|
|
|
int kern_path(const char *name, unsigned int flags, struct path *path)
|
|
{
|
|
struct nameidata nd;
|
|
int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
|
|
if (!res)
|
|
*path = nd.path;
|
|
return res;
|
|
}
|
|
|
|
/**
|
|
* vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
|
|
* @dentry: pointer to dentry of the base directory
|
|
* @mnt: pointer to vfs mount of the base directory
|
|
* @name: pointer to file name
|
|
* @flags: lookup flags
|
|
* @path: pointer to struct path to fill
|
|
*/
|
|
int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
|
|
const char *name, unsigned int flags,
|
|
struct path *path)
|
|
{
|
|
struct nameidata nd;
|
|
int err;
|
|
nd.root.dentry = dentry;
|
|
nd.root.mnt = mnt;
|
|
BUG_ON(flags & LOOKUP_PARENT);
|
|
/* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
|
|
err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
|
|
if (!err)
|
|
*path = nd.path;
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* Restricted form of lookup. Doesn't follow links, single-component only,
|
|
* needs parent already locked. Doesn't follow mounts.
|
|
* SMP-safe.
|
|
*/
|
|
static struct dentry *lookup_hash(struct nameidata *nd)
|
|
{
|
|
return __lookup_hash(&nd->last, nd->path.dentry, nd);
|
|
}
|
|
|
|
/**
|
|
* lookup_one_len - filesystem helper to lookup single pathname component
|
|
* @name: pathname component to lookup
|
|
* @base: base directory to lookup from
|
|
* @len: maximum length @len should be interpreted to
|
|
*
|
|
* Note that this routine is purely a helper for filesystem usage and should
|
|
* not be called by generic code. Also note that by using this function the
|
|
* nameidata argument is passed to the filesystem methods and a filesystem
|
|
* using this helper needs to be prepared for that.
|
|
*/
|
|
struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
|
|
{
|
|
struct qstr this;
|
|
unsigned int c;
|
|
int err;
|
|
|
|
WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
|
|
|
|
this.name = name;
|
|
this.len = len;
|
|
this.hash = full_name_hash(name, len);
|
|
if (!len)
|
|
return ERR_PTR(-EACCES);
|
|
|
|
while (len--) {
|
|
c = *(const unsigned char *)name++;
|
|
if (c == '/' || c == '\0')
|
|
return ERR_PTR(-EACCES);
|
|
}
|
|
/*
|
|
* See if the low-level filesystem might want
|
|
* to use its own hash..
|
|
*/
|
|
if (base->d_flags & DCACHE_OP_HASH) {
|
|
int err = base->d_op->d_hash(base, base->d_inode, &this);
|
|
if (err < 0)
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
err = inode_permission(base->d_inode, MAY_EXEC);
|
|
if (err)
|
|
return ERR_PTR(err);
|
|
|
|
return __lookup_hash(&this, base, NULL);
|
|
}
|
|
|
|
int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
|
|
struct path *path, int *empty)
|
|
{
|
|
struct nameidata nd;
|
|
char *tmp = getname_flags(name, flags, empty);
|
|
int err = PTR_ERR(tmp);
|
|
if (!IS_ERR(tmp)) {
|
|
|
|
BUG_ON(flags & LOOKUP_PARENT);
|
|
|
|
err = do_path_lookup(dfd, tmp, flags, &nd);
|
|
putname(tmp);
|
|
if (!err)
|
|
*path = nd.path;
|
|
}
|
|
return err;
|
|
}
|
|
|
|
int user_path_at(int dfd, const char __user *name, unsigned flags,
|
|
struct path *path)
|
|
{
|
|
return user_path_at_empty(dfd, name, flags, path, NULL);
|
|
}
|
|
|
|
static int user_path_parent(int dfd, const char __user *path,
|
|
struct nameidata *nd, char **name)
|
|
{
|
|
char *s = getname(path);
|
|
int error;
|
|
|
|
if (IS_ERR(s))
|
|
return PTR_ERR(s);
|
|
|
|
error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
|
|
if (error)
|
|
putname(s);
|
|
else
|
|
*name = s;
|
|
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* It's inline, so penalty for filesystems that don't use sticky bit is
|
|
* minimal.
|
|
*/
|
|
static inline int check_sticky(struct inode *dir, struct inode *inode)
|
|
{
|
|
uid_t fsuid = current_fsuid();
|
|
|
|
if (!(dir->i_mode & S_ISVTX))
|
|
return 0;
|
|
if (current_user_ns() != inode_userns(inode))
|
|
goto other_userns;
|
|
if (inode->i_uid == fsuid)
|
|
return 0;
|
|
if (dir->i_uid == fsuid)
|
|
return 0;
|
|
|
|
other_userns:
|
|
return !ns_capable(inode_userns(inode), CAP_FOWNER);
|
|
}
|
|
|
|
/*
|
|
* Check whether we can remove a link victim from directory dir, check
|
|
* whether the type of victim is right.
|
|
* 1. We can't do it if dir is read-only (done in permission())
|
|
* 2. We should have write and exec permissions on dir
|
|
* 3. We can't remove anything from append-only dir
|
|
* 4. We can't do anything with immutable dir (done in permission())
|
|
* 5. If the sticky bit on dir is set we should either
|
|
* a. be owner of dir, or
|
|
* b. be owner of victim, or
|
|
* c. have CAP_FOWNER capability
|
|
* 6. If the victim is append-only or immutable we can't do antyhing with
|
|
* links pointing to it.
|
|
* 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
|
|
* 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
|
|
* 9. We can't remove a root or mountpoint.
|
|
* 10. We don't allow removal of NFS sillyrenamed files; it's handled by
|
|
* nfs_async_unlink().
|
|
*/
|
|
static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
|
|
{
|
|
int error;
|
|
|
|
if (!victim->d_inode)
|
|
return -ENOENT;
|
|
|
|
BUG_ON(victim->d_parent->d_inode != dir);
|
|
audit_inode_child(victim, dir);
|
|
|
|
error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
|
|
if (error)
|
|
return error;
|
|
if (IS_APPEND(dir))
|
|
return -EPERM;
|
|
if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
|
|
IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
|
|
return -EPERM;
|
|
if (isdir) {
|
|
if (!S_ISDIR(victim->d_inode->i_mode))
|
|
return -ENOTDIR;
|
|
if (IS_ROOT(victim))
|
|
return -EBUSY;
|
|
} else if (S_ISDIR(victim->d_inode->i_mode))
|
|
return -EISDIR;
|
|
if (IS_DEADDIR(dir))
|
|
return -ENOENT;
|
|
if (victim->d_flags & DCACHE_NFSFS_RENAMED)
|
|
return -EBUSY;
|
|
return 0;
|
|
}
|
|
|
|
/* Check whether we can create an object with dentry child in directory
|
|
* dir.
|
|
* 1. We can't do it if child already exists (open has special treatment for
|
|
* this case, but since we are inlined it's OK)
|
|
* 2. We can't do it if dir is read-only (done in permission())
|
|
* 3. We should have write and exec permissions on dir
|
|
* 4. We can't do it if dir is immutable (done in permission())
|
|
*/
|
|
static inline int may_create(struct inode *dir, struct dentry *child)
|
|
{
|
|
if (child->d_inode)
|
|
return -EEXIST;
|
|
if (IS_DEADDIR(dir))
|
|
return -ENOENT;
|
|
return inode_permission(dir, MAY_WRITE | MAY_EXEC);
|
|
}
|
|
|
|
/*
|
|
* p1 and p2 should be directories on the same fs.
|
|
*/
|
|
struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
|
|
{
|
|
struct dentry *p;
|
|
|
|
if (p1 == p2) {
|
|
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
|
|
return NULL;
|
|
}
|
|
|
|
mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
|
|
|
|
p = d_ancestor(p2, p1);
|
|
if (p) {
|
|
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
|
|
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
|
|
return p;
|
|
}
|
|
|
|
p = d_ancestor(p1, p2);
|
|
if (p) {
|
|
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
|
|
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
|
|
return p;
|
|
}
|
|
|
|
mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
|
|
mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
|
|
return NULL;
|
|
}
|
|
|
|
void unlock_rename(struct dentry *p1, struct dentry *p2)
|
|
{
|
|
mutex_unlock(&p1->d_inode->i_mutex);
|
|
if (p1 != p2) {
|
|
mutex_unlock(&p2->d_inode->i_mutex);
|
|
mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
|
|
}
|
|
}
|
|
|
|
int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
|
|
struct nameidata *nd)
|
|
{
|
|
int error = may_create(dir, dentry);
|
|
|
|
if (error)
|
|
return error;
|
|
|
|
if (!dir->i_op->create)
|
|
return -EACCES; /* shouldn't it be ENOSYS? */
|
|
mode &= S_IALLUGO;
|
|
mode |= S_IFREG;
|
|
error = security_inode_create(dir, dentry, mode);
|
|
if (error)
|
|
return error;
|
|
error = dir->i_op->create(dir, dentry, mode, nd);
|
|
if (!error)
|
|
fsnotify_create(dir, dentry);
|
|
return error;
|
|
}
|
|
|
|
static int may_open(struct path *path, int acc_mode, int flag)
|
|
{
|
|
struct dentry *dentry = path->dentry;
|
|
struct inode *inode = dentry->d_inode;
|
|
int error;
|
|
|
|
/* O_PATH? */
|
|
if (!acc_mode)
|
|
return 0;
|
|
|
|
if (!inode)
|
|
return -ENOENT;
|
|
|
|
switch (inode->i_mode & S_IFMT) {
|
|
case S_IFLNK:
|
|
return -ELOOP;
|
|
case S_IFDIR:
|
|
if (acc_mode & MAY_WRITE)
|
|
return -EISDIR;
|
|
break;
|
|
case S_IFBLK:
|
|
case S_IFCHR:
|
|
if (path->mnt->mnt_flags & MNT_NODEV)
|
|
return -EACCES;
|
|
/*FALLTHRU*/
|
|
case S_IFIFO:
|
|
case S_IFSOCK:
|
|
flag &= ~O_TRUNC;
|
|
break;
|
|
}
|
|
|
|
error = inode_permission(inode, acc_mode);
|
|
if (error)
|
|
return error;
|
|
|
|
/*
|
|
* An append-only file must be opened in append mode for writing.
|
|
*/
|
|
if (IS_APPEND(inode)) {
|
|
if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
|
|
return -EPERM;
|
|
if (flag & O_TRUNC)
|
|
return -EPERM;
|
|
}
|
|
|
|
/* O_NOATIME can only be set by the owner or superuser */
|
|
if (flag & O_NOATIME && !inode_owner_or_capable(inode))
|
|
return -EPERM;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int handle_truncate(struct file *filp)
|
|
{
|
|
struct path *path = &filp->f_path;
|
|
struct inode *inode = path->dentry->d_inode;
|
|
int error = get_write_access(inode);
|
|
if (error)
|
|
return error;
|
|
/*
|
|
* Refuse to truncate files with mandatory locks held on them.
|
|
*/
|
|
error = locks_verify_locked(inode);
|
|
if (!error)
|
|
error = security_path_truncate(path);
|
|
if (!error) {
|
|
error = do_truncate(path->dentry, 0,
|
|
ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
|
|
filp);
|
|
}
|
|
put_write_access(inode);
|
|
return error;
|
|
}
|
|
|
|
static inline int open_to_namei_flags(int flag)
|
|
{
|
|
if ((flag & O_ACCMODE) == 3)
|
|
flag--;
|
|
return flag;
|
|
}
|
|
|
|
/*
|
|
* Handle the last step of open()
|
|
*/
|
|
static struct file *do_last(struct nameidata *nd, struct path *path,
|
|
const struct open_flags *op, const char *pathname)
|
|
{
|
|
struct dentry *dir = nd->path.dentry;
|
|
struct dentry *dentry;
|
|
int open_flag = op->open_flag;
|
|
int will_truncate = open_flag & O_TRUNC;
|
|
int want_write = 0;
|
|
int acc_mode = op->acc_mode;
|
|
struct file *filp;
|
|
int error;
|
|
|
|
nd->flags &= ~LOOKUP_PARENT;
|
|
nd->flags |= op->intent;
|
|
|
|
switch (nd->last_type) {
|
|
case LAST_DOTDOT:
|
|
case LAST_DOT:
|
|
error = handle_dots(nd, nd->last_type);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
/* fallthrough */
|
|
case LAST_ROOT:
|
|
error = complete_walk(nd);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
audit_inode(pathname, nd->path.dentry);
|
|
if (open_flag & O_CREAT) {
|
|
error = -EISDIR;
|
|
goto exit;
|
|
}
|
|
goto ok;
|
|
case LAST_BIND:
|
|
error = complete_walk(nd);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
audit_inode(pathname, dir);
|
|
goto ok;
|
|
}
|
|
|
|
if (!(open_flag & O_CREAT)) {
|
|
int symlink_ok = 0;
|
|
if (nd->last.name[nd->last.len])
|
|
nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
|
|
if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
|
|
symlink_ok = 1;
|
|
/* we _can_ be in RCU mode here */
|
|
error = walk_component(nd, path, &nd->last, LAST_NORM,
|
|
!symlink_ok);
|
|
if (error < 0)
|
|
return ERR_PTR(error);
|
|
if (error) /* symlink */
|
|
return NULL;
|
|
/* sayonara */
|
|
error = complete_walk(nd);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
|
|
error = -ENOTDIR;
|
|
if (nd->flags & LOOKUP_DIRECTORY) {
|
|
if (!nd->inode->i_op->lookup)
|
|
goto exit;
|
|
}
|
|
audit_inode(pathname, nd->path.dentry);
|
|
goto ok;
|
|
}
|
|
|
|
/* create side of things */
|
|
/*
|
|
* This will *only* deal with leaving RCU mode - LOOKUP_JUMPED has been
|
|
* cleared when we got to the last component we are about to look up
|
|
*/
|
|
error = complete_walk(nd);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
|
|
audit_inode(pathname, dir);
|
|
error = -EISDIR;
|
|
/* trailing slashes? */
|
|
if (nd->last.name[nd->last.len])
|
|
goto exit;
|
|
|
|
mutex_lock(&dir->d_inode->i_mutex);
|
|
|
|
dentry = lookup_hash(nd);
|
|
error = PTR_ERR(dentry);
|
|
if (IS_ERR(dentry)) {
|
|
mutex_unlock(&dir->d_inode->i_mutex);
|
|
goto exit;
|
|
}
|
|
|
|
path->dentry = dentry;
|
|
path->mnt = nd->path.mnt;
|
|
|
|
/* Negative dentry, just create the file */
|
|
if (!dentry->d_inode) {
|
|
umode_t mode = op->mode;
|
|
if (!IS_POSIXACL(dir->d_inode))
|
|
mode &= ~current_umask();
|
|
/*
|
|
* This write is needed to ensure that a
|
|
* rw->ro transition does not occur between
|
|
* the time when the file is created and when
|
|
* a permanent write count is taken through
|
|
* the 'struct file' in nameidata_to_filp().
|
|
*/
|
|
error = mnt_want_write(nd->path.mnt);
|
|
if (error)
|
|
goto exit_mutex_unlock;
|
|
want_write = 1;
|
|
/* Don't check for write permission, don't truncate */
|
|
open_flag &= ~O_TRUNC;
|
|
will_truncate = 0;
|
|
acc_mode = MAY_OPEN;
|
|
error = security_path_mknod(&nd->path, dentry, mode, 0);
|
|
if (error)
|
|
goto exit_mutex_unlock;
|
|
error = vfs_create(dir->d_inode, dentry, mode, nd);
|
|
if (error)
|
|
goto exit_mutex_unlock;
|
|
mutex_unlock(&dir->d_inode->i_mutex);
|
|
dput(nd->path.dentry);
|
|
nd->path.dentry = dentry;
|
|
goto common;
|
|
}
|
|
|
|
/*
|
|
* It already exists.
|
|
*/
|
|
mutex_unlock(&dir->d_inode->i_mutex);
|
|
audit_inode(pathname, path->dentry);
|
|
|
|
error = -EEXIST;
|
|
if (open_flag & O_EXCL)
|
|
goto exit_dput;
|
|
|
|
error = follow_managed(path, nd->flags);
|
|
if (error < 0)
|
|
goto exit_dput;
|
|
|
|
if (error)
|
|
nd->flags |= LOOKUP_JUMPED;
|
|
|
|
error = -ENOENT;
|
|
if (!path->dentry->d_inode)
|
|
goto exit_dput;
|
|
|
|
if (path->dentry->d_inode->i_op->follow_link)
|
|
return NULL;
|
|
|
|
path_to_nameidata(path, nd);
|
|
nd->inode = path->dentry->d_inode;
|
|
/* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
|
|
error = complete_walk(nd);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
error = -EISDIR;
|
|
if (S_ISDIR(nd->inode->i_mode))
|
|
goto exit;
|
|
ok:
|
|
if (!S_ISREG(nd->inode->i_mode))
|
|
will_truncate = 0;
|
|
|
|
if (will_truncate) {
|
|
error = mnt_want_write(nd->path.mnt);
|
|
if (error)
|
|
goto exit;
|
|
want_write = 1;
|
|
}
|
|
common:
|
|
error = may_open(&nd->path, acc_mode, open_flag);
|
|
if (error)
|
|
goto exit;
|
|
filp = nameidata_to_filp(nd);
|
|
if (!IS_ERR(filp)) {
|
|
error = ima_file_check(filp, op->acc_mode);
|
|
if (error) {
|
|
fput(filp);
|
|
filp = ERR_PTR(error);
|
|
}
|
|
}
|
|
if (!IS_ERR(filp)) {
|
|
if (will_truncate) {
|
|
error = handle_truncate(filp);
|
|
if (error) {
|
|
fput(filp);
|
|
filp = ERR_PTR(error);
|
|
}
|
|
}
|
|
}
|
|
out:
|
|
if (want_write)
|
|
mnt_drop_write(nd->path.mnt);
|
|
path_put(&nd->path);
|
|
return filp;
|
|
|
|
exit_mutex_unlock:
|
|
mutex_unlock(&dir->d_inode->i_mutex);
|
|
exit_dput:
|
|
path_put_conditional(path, nd);
|
|
exit:
|
|
filp = ERR_PTR(error);
|
|
goto out;
|
|
}
|
|
|
|
static struct file *path_openat(int dfd, const char *pathname,
|
|
struct nameidata *nd, const struct open_flags *op, int flags)
|
|
{
|
|
struct file *base = NULL;
|
|
struct file *filp;
|
|
struct path path;
|
|
int error;
|
|
|
|
filp = get_empty_filp();
|
|
if (!filp)
|
|
return ERR_PTR(-ENFILE);
|
|
|
|
filp->f_flags = op->open_flag;
|
|
nd->intent.open.file = filp;
|
|
nd->intent.open.flags = open_to_namei_flags(op->open_flag);
|
|
nd->intent.open.create_mode = op->mode;
|
|
|
|
error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base);
|
|
if (unlikely(error))
|
|
goto out_filp;
|
|
|
|
current->total_link_count = 0;
|
|
error = link_path_walk(pathname, nd);
|
|
if (unlikely(error))
|
|
goto out_filp;
|
|
|
|
filp = do_last(nd, &path, op, pathname);
|
|
while (unlikely(!filp)) { /* trailing symlink */
|
|
struct path link = path;
|
|
void *cookie;
|
|
if (!(nd->flags & LOOKUP_FOLLOW)) {
|
|
path_put_conditional(&path, nd);
|
|
path_put(&nd->path);
|
|
filp = ERR_PTR(-ELOOP);
|
|
break;
|
|
}
|
|
nd->flags |= LOOKUP_PARENT;
|
|
nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
|
|
error = follow_link(&link, nd, &cookie);
|
|
if (unlikely(error))
|
|
filp = ERR_PTR(error);
|
|
else
|
|
filp = do_last(nd, &path, op, pathname);
|
|
put_link(nd, &link, cookie);
|
|
}
|
|
out:
|
|
if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
|
|
path_put(&nd->root);
|
|
if (base)
|
|
fput(base);
|
|
release_open_intent(nd);
|
|
return filp;
|
|
|
|
out_filp:
|
|
filp = ERR_PTR(error);
|
|
goto out;
|
|
}
|
|
|
|
struct file *do_filp_open(int dfd, const char *pathname,
|
|
const struct open_flags *op, int flags)
|
|
{
|
|
struct nameidata nd;
|
|
struct file *filp;
|
|
|
|
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
|
|
if (unlikely(filp == ERR_PTR(-ECHILD)))
|
|
filp = path_openat(dfd, pathname, &nd, op, flags);
|
|
if (unlikely(filp == ERR_PTR(-ESTALE)))
|
|
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
|
|
return filp;
|
|
}
|
|
|
|
struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
|
|
const char *name, const struct open_flags *op, int flags)
|
|
{
|
|
struct nameidata nd;
|
|
struct file *file;
|
|
|
|
nd.root.mnt = mnt;
|
|
nd.root.dentry = dentry;
|
|
|
|
flags |= LOOKUP_ROOT;
|
|
|
|
if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
|
|
return ERR_PTR(-ELOOP);
|
|
|
|
file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU);
|
|
if (unlikely(file == ERR_PTR(-ECHILD)))
|
|
file = path_openat(-1, name, &nd, op, flags);
|
|
if (unlikely(file == ERR_PTR(-ESTALE)))
|
|
file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL);
|
|
return file;
|
|
}
|
|
|
|
struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path, int is_dir)
|
|
{
|
|
struct dentry *dentry = ERR_PTR(-EEXIST);
|
|
struct nameidata nd;
|
|
int error = do_path_lookup(dfd, pathname, LOOKUP_PARENT, &nd);
|
|
if (error)
|
|
return ERR_PTR(error);
|
|
|
|
/*
|
|
* Yucky last component or no last component at all?
|
|
* (foo/., foo/.., /////)
|
|
*/
|
|
if (nd.last_type != LAST_NORM)
|
|
goto out;
|
|
nd.flags &= ~LOOKUP_PARENT;
|
|
nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
|
|
nd.intent.open.flags = O_EXCL;
|
|
|
|
/*
|
|
* Do the final lookup.
|
|
*/
|
|
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
|
|
dentry = lookup_hash(&nd);
|
|
if (IS_ERR(dentry))
|
|
goto fail;
|
|
|
|
if (dentry->d_inode)
|
|
goto eexist;
|
|
/*
|
|
* Special case - lookup gave negative, but... we had foo/bar/
|
|
* From the vfs_mknod() POV we just have a negative dentry -
|
|
* all is fine. Let's be bastards - you had / on the end, you've
|
|
* been asking for (non-existent) directory. -ENOENT for you.
|
|
*/
|
|
if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
|
|
dput(dentry);
|
|
dentry = ERR_PTR(-ENOENT);
|
|
goto fail;
|
|
}
|
|
*path = nd.path;
|
|
return dentry;
|
|
eexist:
|
|
dput(dentry);
|
|
dentry = ERR_PTR(-EEXIST);
|
|
fail:
|
|
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
|
|
out:
|
|
path_put(&nd.path);
|
|
return dentry;
|
|
}
|
|
EXPORT_SYMBOL(kern_path_create);
|
|
|
|
struct dentry *user_path_create(int dfd, const char __user *pathname, struct path *path, int is_dir)
|
|
{
|
|
char *tmp = getname(pathname);
|
|
struct dentry *res;
|
|
if (IS_ERR(tmp))
|
|
return ERR_CAST(tmp);
|
|
res = kern_path_create(dfd, tmp, path, is_dir);
|
|
putname(tmp);
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(user_path_create);
|
|
|
|
int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
|
|
{
|
|
int error = may_create(dir, dentry);
|
|
|
|
if (error)
|
|
return error;
|
|
|
|
if ((S_ISCHR(mode) || S_ISBLK(mode)) &&
|
|
!ns_capable(inode_userns(dir), CAP_MKNOD))
|
|
return -EPERM;
|
|
|
|
if (!dir->i_op->mknod)
|
|
return -EPERM;
|
|
|
|
error = devcgroup_inode_mknod(mode, dev);
|
|
if (error)
|
|
return error;
|
|
|
|
error = security_inode_mknod(dir, dentry, mode, dev);
|
|
if (error)
|
|
return error;
|
|
|
|
error = dir->i_op->mknod(dir, dentry, mode, dev);
|
|
if (!error)
|
|
fsnotify_create(dir, dentry);
|
|
return error;
|
|
}
|
|
|
|
static int may_mknod(umode_t mode)
|
|
{
|
|
switch (mode & S_IFMT) {
|
|
case S_IFREG:
|
|
case S_IFCHR:
|
|
case S_IFBLK:
|
|
case S_IFIFO:
|
|
case S_IFSOCK:
|
|
case 0: /* zero mode translates to S_IFREG */
|
|
return 0;
|
|
case S_IFDIR:
|
|
return -EPERM;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
|
|
unsigned, dev)
|
|
{
|
|
struct dentry *dentry;
|
|
struct path path;
|
|
int error;
|
|
|
|
if (S_ISDIR(mode))
|
|
return -EPERM;
|
|
|
|
dentry = user_path_create(dfd, filename, &path, 0);
|
|
if (IS_ERR(dentry))
|
|
return PTR_ERR(dentry);
|
|
|
|
if (!IS_POSIXACL(path.dentry->d_inode))
|
|
mode &= ~current_umask();
|
|
error = may_mknod(mode);
|
|
if (error)
|
|
goto out_dput;
|
|
error = mnt_want_write(path.mnt);
|
|
if (error)
|
|
goto out_dput;
|
|
error = security_path_mknod(&path, dentry, mode, dev);
|
|
if (error)
|
|
goto out_drop_write;
|
|
switch (mode & S_IFMT) {
|
|
case 0: case S_IFREG:
|
|
error = vfs_create(path.dentry->d_inode,dentry,mode,NULL);
|
|
break;
|
|
case S_IFCHR: case S_IFBLK:
|
|
error = vfs_mknod(path.dentry->d_inode,dentry,mode,
|
|
new_decode_dev(dev));
|
|
break;
|
|
case S_IFIFO: case S_IFSOCK:
|
|
error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
|
|
break;
|
|
}
|
|
out_drop_write:
|
|
mnt_drop_write(path.mnt);
|
|
out_dput:
|
|
dput(dentry);
|
|
mutex_unlock(&path.dentry->d_inode->i_mutex);
|
|
path_put(&path);
|
|
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
|
|
{
|
|
return sys_mknodat(AT_FDCWD, filename, mode, dev);
|
|
}
|
|
|
|
int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
|
|
{
|
|
int error = may_create(dir, dentry);
|
|
unsigned max_links = dir->i_sb->s_max_links;
|
|
|
|
if (error)
|
|
return error;
|
|
|
|
if (!dir->i_op->mkdir)
|
|
return -EPERM;
|
|
|
|
mode &= (S_IRWXUGO|S_ISVTX);
|
|
error = security_inode_mkdir(dir, dentry, mode);
|
|
if (error)
|
|
return error;
|
|
|
|
if (max_links && dir->i_nlink >= max_links)
|
|
return -EMLINK;
|
|
|
|
error = dir->i_op->mkdir(dir, dentry, mode);
|
|
if (!error)
|
|
fsnotify_mkdir(dir, dentry);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
|
|
{
|
|
struct dentry *dentry;
|
|
struct path path;
|
|
int error;
|
|
|
|
dentry = user_path_create(dfd, pathname, &path, 1);
|
|
if (IS_ERR(dentry))
|
|
return PTR_ERR(dentry);
|
|
|
|
if (!IS_POSIXACL(path.dentry->d_inode))
|
|
mode &= ~current_umask();
|
|
error = mnt_want_write(path.mnt);
|
|
if (error)
|
|
goto out_dput;
|
|
error = security_path_mkdir(&path, dentry, mode);
|
|
if (error)
|
|
goto out_drop_write;
|
|
error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
|
|
out_drop_write:
|
|
mnt_drop_write(path.mnt);
|
|
out_dput:
|
|
dput(dentry);
|
|
mutex_unlock(&path.dentry->d_inode->i_mutex);
|
|
path_put(&path);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
|
|
{
|
|
return sys_mkdirat(AT_FDCWD, pathname, mode);
|
|
}
|
|
|
|
/*
|
|
* The dentry_unhash() helper will try to drop the dentry early: we
|
|
* should have a usage count of 1 if we're the only user of this
|
|
* dentry, and if that is true (possibly after pruning the dcache),
|
|
* then we drop the dentry now.
|
|
*
|
|
* A low-level filesystem can, if it choses, legally
|
|
* do a
|
|
*
|
|
* if (!d_unhashed(dentry))
|
|
* return -EBUSY;
|
|
*
|
|
* if it cannot handle the case of removing a directory
|
|
* that is still in use by something else..
|
|
*/
|
|
void dentry_unhash(struct dentry *dentry)
|
|
{
|
|
shrink_dcache_parent(dentry);
|
|
spin_lock(&dentry->d_lock);
|
|
if (dentry->d_count == 1)
|
|
__d_drop(dentry);
|
|
spin_unlock(&dentry->d_lock);
|
|
}
|
|
|
|
int vfs_rmdir(struct inode *dir, struct dentry *dentry)
|
|
{
|
|
int error = may_delete(dir, dentry, 1);
|
|
|
|
if (error)
|
|
return error;
|
|
|
|
if (!dir->i_op->rmdir)
|
|
return -EPERM;
|
|
|
|
dget(dentry);
|
|
mutex_lock(&dentry->d_inode->i_mutex);
|
|
|
|
error = -EBUSY;
|
|
if (d_mountpoint(dentry))
|
|
goto out;
|
|
|
|
error = security_inode_rmdir(dir, dentry);
|
|
if (error)
|
|
goto out;
|
|
|
|
shrink_dcache_parent(dentry);
|
|
error = dir->i_op->rmdir(dir, dentry);
|
|
if (error)
|
|
goto out;
|
|
|
|
dentry->d_inode->i_flags |= S_DEAD;
|
|
dont_mount(dentry);
|
|
|
|
out:
|
|
mutex_unlock(&dentry->d_inode->i_mutex);
|
|
dput(dentry);
|
|
if (!error)
|
|
d_delete(dentry);
|
|
return error;
|
|
}
|
|
|
|
static long do_rmdir(int dfd, const char __user *pathname)
|
|
{
|
|
int error = 0;
|
|
char * name;
|
|
struct dentry *dentry;
|
|
struct nameidata nd;
|
|
|
|
error = user_path_parent(dfd, pathname, &nd, &name);
|
|
if (error)
|
|
return error;
|
|
|
|
switch(nd.last_type) {
|
|
case LAST_DOTDOT:
|
|
error = -ENOTEMPTY;
|
|
goto exit1;
|
|
case LAST_DOT:
|
|
error = -EINVAL;
|
|
goto exit1;
|
|
case LAST_ROOT:
|
|
error = -EBUSY;
|
|
goto exit1;
|
|
}
|
|
|
|
nd.flags &= ~LOOKUP_PARENT;
|
|
|
|
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
|
|
dentry = lookup_hash(&nd);
|
|
error = PTR_ERR(dentry);
|
|
if (IS_ERR(dentry))
|
|
goto exit2;
|
|
if (!dentry->d_inode) {
|
|
error = -ENOENT;
|
|
goto exit3;
|
|
}
|
|
error = mnt_want_write(nd.path.mnt);
|
|
if (error)
|
|
goto exit3;
|
|
error = security_path_rmdir(&nd.path, dentry);
|
|
if (error)
|
|
goto exit4;
|
|
error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
|
|
exit4:
|
|
mnt_drop_write(nd.path.mnt);
|
|
exit3:
|
|
dput(dentry);
|
|
exit2:
|
|
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
|
|
exit1:
|
|
path_put(&nd.path);
|
|
putname(name);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
|
|
{
|
|
return do_rmdir(AT_FDCWD, pathname);
|
|
}
|
|
|
|
int vfs_unlink(struct inode *dir, struct dentry *dentry)
|
|
{
|
|
int error = may_delete(dir, dentry, 0);
|
|
|
|
if (error)
|
|
return error;
|
|
|
|
if (!dir->i_op->unlink)
|
|
return -EPERM;
|
|
|
|
mutex_lock(&dentry->d_inode->i_mutex);
|
|
if (d_mountpoint(dentry))
|
|
error = -EBUSY;
|
|
else {
|
|
error = security_inode_unlink(dir, dentry);
|
|
if (!error) {
|
|
error = dir->i_op->unlink(dir, dentry);
|
|
if (!error)
|
|
dont_mount(dentry);
|
|
}
|
|
}
|
|
mutex_unlock(&dentry->d_inode->i_mutex);
|
|
|
|
/* We don't d_delete() NFS sillyrenamed files--they still exist. */
|
|
if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
|
|
fsnotify_link_count(dentry->d_inode);
|
|
d_delete(dentry);
|
|
}
|
|
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Make sure that the actual truncation of the file will occur outside its
|
|
* directory's i_mutex. Truncate can take a long time if there is a lot of
|
|
* writeout happening, and we don't want to prevent access to the directory
|
|
* while waiting on the I/O.
|
|
*/
|
|
static long do_unlinkat(int dfd, const char __user *pathname)
|
|
{
|
|
int error;
|
|
char *name;
|
|
struct dentry *dentry;
|
|
struct nameidata nd;
|
|
struct inode *inode = NULL;
|
|
|
|
error = user_path_parent(dfd, pathname, &nd, &name);
|
|
if (error)
|
|
return error;
|
|
|
|
error = -EISDIR;
|
|
if (nd.last_type != LAST_NORM)
|
|
goto exit1;
|
|
|
|
nd.flags &= ~LOOKUP_PARENT;
|
|
|
|
mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
|
|
dentry = lookup_hash(&nd);
|
|
error = PTR_ERR(dentry);
|
|
if (!IS_ERR(dentry)) {
|
|
/* Why not before? Because we want correct error value */
|
|
if (nd.last.name[nd.last.len])
|
|
goto slashes;
|
|
inode = dentry->d_inode;
|
|
if (!inode)
|
|
goto slashes;
|
|
ihold(inode);
|
|
error = mnt_want_write(nd.path.mnt);
|
|
if (error)
|
|
goto exit2;
|
|
error = security_path_unlink(&nd.path, dentry);
|
|
if (error)
|
|
goto exit3;
|
|
error = vfs_unlink(nd.path.dentry->d_inode, dentry);
|
|
exit3:
|
|
mnt_drop_write(nd.path.mnt);
|
|
exit2:
|
|
dput(dentry);
|
|
}
|
|
mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
|
|
if (inode)
|
|
iput(inode); /* truncate the inode here */
|
|
exit1:
|
|
path_put(&nd.path);
|
|
putname(name);
|
|
return error;
|
|
|
|
slashes:
|
|
error = !dentry->d_inode ? -ENOENT :
|
|
S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
|
|
goto exit2;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
|
|
{
|
|
if ((flag & ~AT_REMOVEDIR) != 0)
|
|
return -EINVAL;
|
|
|
|
if (flag & AT_REMOVEDIR)
|
|
return do_rmdir(dfd, pathname);
|
|
|
|
return do_unlinkat(dfd, pathname);
|
|
}
|
|
|
|
SYSCALL_DEFINE1(unlink, const char __user *, pathname)
|
|
{
|
|
return do_unlinkat(AT_FDCWD, pathname);
|
|
}
|
|
|
|
int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
|
|
{
|
|
int error = may_create(dir, dentry);
|
|
|
|
if (error)
|
|
return error;
|
|
|
|
if (!dir->i_op->symlink)
|
|
return -EPERM;
|
|
|
|
error = security_inode_symlink(dir, dentry, oldname);
|
|
if (error)
|
|
return error;
|
|
|
|
error = dir->i_op->symlink(dir, dentry, oldname);
|
|
if (!error)
|
|
fsnotify_create(dir, dentry);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
|
|
int, newdfd, const char __user *, newname)
|
|
{
|
|
int error;
|
|
char *from;
|
|
struct dentry *dentry;
|
|
struct path path;
|
|
|
|
from = getname(oldname);
|
|
if (IS_ERR(from))
|
|
return PTR_ERR(from);
|
|
|
|
dentry = user_path_create(newdfd, newname, &path, 0);
|
|
error = PTR_ERR(dentry);
|
|
if (IS_ERR(dentry))
|
|
goto out_putname;
|
|
|
|
error = mnt_want_write(path.mnt);
|
|
if (error)
|
|
goto out_dput;
|
|
error = security_path_symlink(&path, dentry, from);
|
|
if (error)
|
|
goto out_drop_write;
|
|
error = vfs_symlink(path.dentry->d_inode, dentry, from);
|
|
out_drop_write:
|
|
mnt_drop_write(path.mnt);
|
|
out_dput:
|
|
dput(dentry);
|
|
mutex_unlock(&path.dentry->d_inode->i_mutex);
|
|
path_put(&path);
|
|
out_putname:
|
|
putname(from);
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
|
|
{
|
|
return sys_symlinkat(oldname, AT_FDCWD, newname);
|
|
}
|
|
|
|
int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
|
|
{
|
|
struct inode *inode = old_dentry->d_inode;
|
|
unsigned max_links = dir->i_sb->s_max_links;
|
|
int error;
|
|
|
|
if (!inode)
|
|
return -ENOENT;
|
|
|
|
error = may_create(dir, new_dentry);
|
|
if (error)
|
|
return error;
|
|
|
|
if (dir->i_sb != inode->i_sb)
|
|
return -EXDEV;
|
|
|
|
/*
|
|
* A link to an append-only or immutable file cannot be created.
|
|
*/
|
|
if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
|
|
return -EPERM;
|
|
if (!dir->i_op->link)
|
|
return -EPERM;
|
|
if (S_ISDIR(inode->i_mode))
|
|
return -EPERM;
|
|
|
|
error = security_inode_link(old_dentry, dir, new_dentry);
|
|
if (error)
|
|
return error;
|
|
|
|
mutex_lock(&inode->i_mutex);
|
|
/* Make sure we don't allow creating hardlink to an unlinked file */
|
|
if (inode->i_nlink == 0)
|
|
error = -ENOENT;
|
|
else if (max_links && inode->i_nlink >= max_links)
|
|
error = -EMLINK;
|
|
else
|
|
error = dir->i_op->link(old_dentry, dir, new_dentry);
|
|
mutex_unlock(&inode->i_mutex);
|
|
if (!error)
|
|
fsnotify_link(dir, inode, new_dentry);
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Hardlinks are often used in delicate situations. We avoid
|
|
* security-related surprises by not following symlinks on the
|
|
* newname. --KAB
|
|
*
|
|
* We don't follow them on the oldname either to be compatible
|
|
* with linux 2.0, and to avoid hard-linking to directories
|
|
* and other special files. --ADM
|
|
*/
|
|
SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
|
|
int, newdfd, const char __user *, newname, int, flags)
|
|
{
|
|
struct dentry *new_dentry;
|
|
struct path old_path, new_path;
|
|
int how = 0;
|
|
int error;
|
|
|
|
if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
|
|
return -EINVAL;
|
|
/*
|
|
* To use null names we require CAP_DAC_READ_SEARCH
|
|
* This ensures that not everyone will be able to create
|
|
* handlink using the passed filedescriptor.
|
|
*/
|
|
if (flags & AT_EMPTY_PATH) {
|
|
if (!capable(CAP_DAC_READ_SEARCH))
|
|
return -ENOENT;
|
|
how = LOOKUP_EMPTY;
|
|
}
|
|
|
|
if (flags & AT_SYMLINK_FOLLOW)
|
|
how |= LOOKUP_FOLLOW;
|
|
|
|
error = user_path_at(olddfd, oldname, how, &old_path);
|
|
if (error)
|
|
return error;
|
|
|
|
new_dentry = user_path_create(newdfd, newname, &new_path, 0);
|
|
error = PTR_ERR(new_dentry);
|
|
if (IS_ERR(new_dentry))
|
|
goto out;
|
|
|
|
error = -EXDEV;
|
|
if (old_path.mnt != new_path.mnt)
|
|
goto out_dput;
|
|
error = mnt_want_write(new_path.mnt);
|
|
if (error)
|
|
goto out_dput;
|
|
error = security_path_link(old_path.dentry, &new_path, new_dentry);
|
|
if (error)
|
|
goto out_drop_write;
|
|
error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
|
|
out_drop_write:
|
|
mnt_drop_write(new_path.mnt);
|
|
out_dput:
|
|
dput(new_dentry);
|
|
mutex_unlock(&new_path.dentry->d_inode->i_mutex);
|
|
path_put(&new_path);
|
|
out:
|
|
path_put(&old_path);
|
|
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
|
|
{
|
|
return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
|
|
}
|
|
|
|
/*
|
|
* The worst of all namespace operations - renaming directory. "Perverted"
|
|
* doesn't even start to describe it. Somebody in UCB had a heck of a trip...
|
|
* Problems:
|
|
* a) we can get into loop creation. Check is done in is_subdir().
|
|
* b) race potential - two innocent renames can create a loop together.
|
|
* That's where 4.4 screws up. Current fix: serialization on
|
|
* sb->s_vfs_rename_mutex. We might be more accurate, but that's another
|
|
* story.
|
|
* c) we have to lock _three_ objects - parents and victim (if it exists).
|
|
* And that - after we got ->i_mutex on parents (until then we don't know
|
|
* whether the target exists). Solution: try to be smart with locking
|
|
* order for inodes. We rely on the fact that tree topology may change
|
|
* only under ->s_vfs_rename_mutex _and_ that parent of the object we
|
|
* move will be locked. Thus we can rank directories by the tree
|
|
* (ancestors first) and rank all non-directories after them.
|
|
* That works since everybody except rename does "lock parent, lookup,
|
|
* lock child" and rename is under ->s_vfs_rename_mutex.
|
|
* HOWEVER, it relies on the assumption that any object with ->lookup()
|
|
* has no more than 1 dentry. If "hybrid" objects will ever appear,
|
|
* we'd better make sure that there's no link(2) for them.
|
|
* d) conversion from fhandle to dentry may come in the wrong moment - when
|
|
* we are removing the target. Solution: we will have to grab ->i_mutex
|
|
* in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
|
|
* ->i_mutex on parents, which works but leads to some truly excessive
|
|
* locking].
|
|
*/
|
|
static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
|
|
struct inode *new_dir, struct dentry *new_dentry)
|
|
{
|
|
int error = 0;
|
|
struct inode *target = new_dentry->d_inode;
|
|
unsigned max_links = new_dir->i_sb->s_max_links;
|
|
|
|
/*
|
|
* If we are going to change the parent - check write permissions,
|
|
* we'll need to flip '..'.
|
|
*/
|
|
if (new_dir != old_dir) {
|
|
error = inode_permission(old_dentry->d_inode, MAY_WRITE);
|
|
if (error)
|
|
return error;
|
|
}
|
|
|
|
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
|
|
if (error)
|
|
return error;
|
|
|
|
dget(new_dentry);
|
|
if (target)
|
|
mutex_lock(&target->i_mutex);
|
|
|
|
error = -EBUSY;
|
|
if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
|
|
goto out;
|
|
|
|
error = -EMLINK;
|
|
if (max_links && !target && new_dir != old_dir &&
|
|
new_dir->i_nlink >= max_links)
|
|
goto out;
|
|
|
|
if (target)
|
|
shrink_dcache_parent(new_dentry);
|
|
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
|
|
if (error)
|
|
goto out;
|
|
|
|
if (target) {
|
|
target->i_flags |= S_DEAD;
|
|
dont_mount(new_dentry);
|
|
}
|
|
out:
|
|
if (target)
|
|
mutex_unlock(&target->i_mutex);
|
|
dput(new_dentry);
|
|
if (!error)
|
|
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
|
|
d_move(old_dentry,new_dentry);
|
|
return error;
|
|
}
|
|
|
|
static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
|
|
struct inode *new_dir, struct dentry *new_dentry)
|
|
{
|
|
struct inode *target = new_dentry->d_inode;
|
|
int error;
|
|
|
|
error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
|
|
if (error)
|
|
return error;
|
|
|
|
dget(new_dentry);
|
|
if (target)
|
|
mutex_lock(&target->i_mutex);
|
|
|
|
error = -EBUSY;
|
|
if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
|
|
goto out;
|
|
|
|
error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
|
|
if (error)
|
|
goto out;
|
|
|
|
if (target)
|
|
dont_mount(new_dentry);
|
|
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
|
|
d_move(old_dentry, new_dentry);
|
|
out:
|
|
if (target)
|
|
mutex_unlock(&target->i_mutex);
|
|
dput(new_dentry);
|
|
return error;
|
|
}
|
|
|
|
int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
|
|
struct inode *new_dir, struct dentry *new_dentry)
|
|
{
|
|
int error;
|
|
int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
|
|
const unsigned char *old_name;
|
|
|
|
if (old_dentry->d_inode == new_dentry->d_inode)
|
|
return 0;
|
|
|
|
error = may_delete(old_dir, old_dentry, is_dir);
|
|
if (error)
|
|
return error;
|
|
|
|
if (!new_dentry->d_inode)
|
|
error = may_create(new_dir, new_dentry);
|
|
else
|
|
error = may_delete(new_dir, new_dentry, is_dir);
|
|
if (error)
|
|
return error;
|
|
|
|
if (!old_dir->i_op->rename)
|
|
return -EPERM;
|
|
|
|
old_name = fsnotify_oldname_init(old_dentry->d_name.name);
|
|
|
|
if (is_dir)
|
|
error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
|
|
else
|
|
error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
|
|
if (!error)
|
|
fsnotify_move(old_dir, new_dir, old_name, is_dir,
|
|
new_dentry->d_inode, old_dentry);
|
|
fsnotify_oldname_free(old_name);
|
|
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
|
|
int, newdfd, const char __user *, newname)
|
|
{
|
|
struct dentry *old_dir, *new_dir;
|
|
struct dentry *old_dentry, *new_dentry;
|
|
struct dentry *trap;
|
|
struct nameidata oldnd, newnd;
|
|
char *from;
|
|
char *to;
|
|
int error;
|
|
|
|
error = user_path_parent(olddfd, oldname, &oldnd, &from);
|
|
if (error)
|
|
goto exit;
|
|
|
|
error = user_path_parent(newdfd, newname, &newnd, &to);
|
|
if (error)
|
|
goto exit1;
|
|
|
|
error = -EXDEV;
|
|
if (oldnd.path.mnt != newnd.path.mnt)
|
|
goto exit2;
|
|
|
|
old_dir = oldnd.path.dentry;
|
|
error = -EBUSY;
|
|
if (oldnd.last_type != LAST_NORM)
|
|
goto exit2;
|
|
|
|
new_dir = newnd.path.dentry;
|
|
if (newnd.last_type != LAST_NORM)
|
|
goto exit2;
|
|
|
|
oldnd.flags &= ~LOOKUP_PARENT;
|
|
newnd.flags &= ~LOOKUP_PARENT;
|
|
newnd.flags |= LOOKUP_RENAME_TARGET;
|
|
|
|
trap = lock_rename(new_dir, old_dir);
|
|
|
|
old_dentry = lookup_hash(&oldnd);
|
|
error = PTR_ERR(old_dentry);
|
|
if (IS_ERR(old_dentry))
|
|
goto exit3;
|
|
/* source must exist */
|
|
error = -ENOENT;
|
|
if (!old_dentry->d_inode)
|
|
goto exit4;
|
|
/* unless the source is a directory trailing slashes give -ENOTDIR */
|
|
if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
|
|
error = -ENOTDIR;
|
|
if (oldnd.last.name[oldnd.last.len])
|
|
goto exit4;
|
|
if (newnd.last.name[newnd.last.len])
|
|
goto exit4;
|
|
}
|
|
/* source should not be ancestor of target */
|
|
error = -EINVAL;
|
|
if (old_dentry == trap)
|
|
goto exit4;
|
|
new_dentry = lookup_hash(&newnd);
|
|
error = PTR_ERR(new_dentry);
|
|
if (IS_ERR(new_dentry))
|
|
goto exit4;
|
|
/* target should not be an ancestor of source */
|
|
error = -ENOTEMPTY;
|
|
if (new_dentry == trap)
|
|
goto exit5;
|
|
|
|
error = mnt_want_write(oldnd.path.mnt);
|
|
if (error)
|
|
goto exit5;
|
|
error = security_path_rename(&oldnd.path, old_dentry,
|
|
&newnd.path, new_dentry);
|
|
if (error)
|
|
goto exit6;
|
|
error = vfs_rename(old_dir->d_inode, old_dentry,
|
|
new_dir->d_inode, new_dentry);
|
|
exit6:
|
|
mnt_drop_write(oldnd.path.mnt);
|
|
exit5:
|
|
dput(new_dentry);
|
|
exit4:
|
|
dput(old_dentry);
|
|
exit3:
|
|
unlock_rename(new_dir, old_dir);
|
|
exit2:
|
|
path_put(&newnd.path);
|
|
putname(to);
|
|
exit1:
|
|
path_put(&oldnd.path);
|
|
putname(from);
|
|
exit:
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
|
|
{
|
|
return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
|
|
}
|
|
|
|
int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
|
|
{
|
|
int len;
|
|
|
|
len = PTR_ERR(link);
|
|
if (IS_ERR(link))
|
|
goto out;
|
|
|
|
len = strlen(link);
|
|
if (len > (unsigned) buflen)
|
|
len = buflen;
|
|
if (copy_to_user(buffer, link, len))
|
|
len = -EFAULT;
|
|
out:
|
|
return len;
|
|
}
|
|
|
|
/*
|
|
* A helper for ->readlink(). This should be used *ONLY* for symlinks that
|
|
* have ->follow_link() touching nd only in nd_set_link(). Using (or not
|
|
* using) it for any given inode is up to filesystem.
|
|
*/
|
|
int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
|
|
{
|
|
struct nameidata nd;
|
|
void *cookie;
|
|
int res;
|
|
|
|
nd.depth = 0;
|
|
cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
|
|
if (IS_ERR(cookie))
|
|
return PTR_ERR(cookie);
|
|
|
|
res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
|
|
if (dentry->d_inode->i_op->put_link)
|
|
dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
|
|
return res;
|
|
}
|
|
|
|
int vfs_follow_link(struct nameidata *nd, const char *link)
|
|
{
|
|
return __vfs_follow_link(nd, link);
|
|
}
|
|
|
|
/* get the link contents into pagecache */
|
|
static char *page_getlink(struct dentry * dentry, struct page **ppage)
|
|
{
|
|
char *kaddr;
|
|
struct page *page;
|
|
struct address_space *mapping = dentry->d_inode->i_mapping;
|
|
page = read_mapping_page(mapping, 0, NULL);
|
|
if (IS_ERR(page))
|
|
return (char*)page;
|
|
*ppage = page;
|
|
kaddr = kmap(page);
|
|
nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
|
|
return kaddr;
|
|
}
|
|
|
|
int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
|
|
{
|
|
struct page *page = NULL;
|
|
char *s = page_getlink(dentry, &page);
|
|
int res = vfs_readlink(dentry,buffer,buflen,s);
|
|
if (page) {
|
|
kunmap(page);
|
|
page_cache_release(page);
|
|
}
|
|
return res;
|
|
}
|
|
|
|
void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
|
|
{
|
|
struct page *page = NULL;
|
|
nd_set_link(nd, page_getlink(dentry, &page));
|
|
return page;
|
|
}
|
|
|
|
void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
|
|
{
|
|
struct page *page = cookie;
|
|
|
|
if (page) {
|
|
kunmap(page);
|
|
page_cache_release(page);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
|
|
*/
|
|
int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
|
|
{
|
|
struct address_space *mapping = inode->i_mapping;
|
|
struct page *page;
|
|
void *fsdata;
|
|
int err;
|
|
char *kaddr;
|
|
unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
|
|
if (nofs)
|
|
flags |= AOP_FLAG_NOFS;
|
|
|
|
retry:
|
|
err = pagecache_write_begin(NULL, mapping, 0, len-1,
|
|
flags, &page, &fsdata);
|
|
if (err)
|
|
goto fail;
|
|
|
|
kaddr = kmap_atomic(page);
|
|
memcpy(kaddr, symname, len-1);
|
|
kunmap_atomic(kaddr);
|
|
|
|
err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
|
|
page, fsdata);
|
|
if (err < 0)
|
|
goto fail;
|
|
if (err < len-1)
|
|
goto retry;
|
|
|
|
mark_inode_dirty(inode);
|
|
return 0;
|
|
fail:
|
|
return err;
|
|
}
|
|
|
|
int page_symlink(struct inode *inode, const char *symname, int len)
|
|
{
|
|
return __page_symlink(inode, symname, len,
|
|
!(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
|
|
}
|
|
|
|
const struct inode_operations page_symlink_inode_operations = {
|
|
.readlink = generic_readlink,
|
|
.follow_link = page_follow_link_light,
|
|
.put_link = page_put_link,
|
|
};
|
|
|
|
EXPORT_SYMBOL(user_path_at);
|
|
EXPORT_SYMBOL(follow_down_one);
|
|
EXPORT_SYMBOL(follow_down);
|
|
EXPORT_SYMBOL(follow_up);
|
|
EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
|
|
EXPORT_SYMBOL(getname);
|
|
EXPORT_SYMBOL(lock_rename);
|
|
EXPORT_SYMBOL(lookup_one_len);
|
|
EXPORT_SYMBOL(page_follow_link_light);
|
|
EXPORT_SYMBOL(page_put_link);
|
|
EXPORT_SYMBOL(page_readlink);
|
|
EXPORT_SYMBOL(__page_symlink);
|
|
EXPORT_SYMBOL(page_symlink);
|
|
EXPORT_SYMBOL(page_symlink_inode_operations);
|
|
EXPORT_SYMBOL(kern_path);
|
|
EXPORT_SYMBOL(vfs_path_lookup);
|
|
EXPORT_SYMBOL(inode_permission);
|
|
EXPORT_SYMBOL(unlock_rename);
|
|
EXPORT_SYMBOL(vfs_create);
|
|
EXPORT_SYMBOL(vfs_follow_link);
|
|
EXPORT_SYMBOL(vfs_link);
|
|
EXPORT_SYMBOL(vfs_mkdir);
|
|
EXPORT_SYMBOL(vfs_mknod);
|
|
EXPORT_SYMBOL(generic_permission);
|
|
EXPORT_SYMBOL(vfs_readlink);
|
|
EXPORT_SYMBOL(vfs_rename);
|
|
EXPORT_SYMBOL(vfs_rmdir);
|
|
EXPORT_SYMBOL(vfs_symlink);
|
|
EXPORT_SYMBOL(vfs_unlink);
|
|
EXPORT_SYMBOL(dentry_unhash);
|
|
EXPORT_SYMBOL(generic_readlink);
|