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linux/fs/ocfs2/acl.c
Christian Brauner 138060ba92
fs: pass dentry to set acl method 
The current way of setting and getting posix acls through the generic
xattr interface is error prone and type unsafe. The vfs needs to
interpret and fixup posix acls before storing or reporting it to
userspace. Various hacks exist to make this work. The code is hard to
understand and difficult to maintain in it's current form. Instead of
making this work by hacking posix acls through xattr handlers we are
building a dedicated posix acl api around the get and set inode
operations. This removes a lot of hackiness and makes the codepaths
easier to maintain. A lot of background can be found in [1].

Since some filesystem rely on the dentry being available to them when
setting posix acls (e.g., 9p and cifs) they cannot rely on set acl inode
operation. But since ->set_acl() is required in order to use the generic
posix acl xattr handlers filesystems that do not implement this inode
operation cannot use the handler and need to implement their own
dedicated posix acl handlers.

Update the ->set_acl() inode method to take a dentry argument. This
allows all filesystems to rely on ->set_acl().

As far as I can tell all codepaths can be switched to rely on the dentry
instead of just the inode. Note that the original motivation for passing
the dentry separate from the inode instead of just the dentry in the
xattr handlers was because of security modules that call
security_d_instantiate(). This hook is called during
d_instantiate_new(), d_add(), __d_instantiate_anon(), and
d_splice_alias() to initialize the inode's security context and possibly
to set security.* xattrs. Since this only affects security.* xattrs this
is completely irrelevant for posix acls.

Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-10-19 12:55:42 +02:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* acl.c
*
* Copyright (C) 2004, 2008 Oracle. All rights reserved.
*
* CREDITS:
* Lots of code in this file is copy from linux/fs/ext3/acl.c.
* Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <cluster/masklog.h>
#include "ocfs2.h"
#include "alloc.h"
#include "dlmglue.h"
#include "file.h"
#include "inode.h"
#include "journal.h"
#include "ocfs2_fs.h"
#include "xattr.h"
#include "acl.h"
/*
* Convert from xattr value to acl struct.
*/
static struct posix_acl *ocfs2_acl_from_xattr(const void *value, size_t size)
{
int n, count;
struct posix_acl *acl;
if (!value)
return NULL;
if (size < sizeof(struct posix_acl_entry))
return ERR_PTR(-EINVAL);
count = size / sizeof(struct posix_acl_entry);
acl = posix_acl_alloc(count, GFP_NOFS);
if (!acl)
return ERR_PTR(-ENOMEM);
for (n = 0; n < count; n++) {
struct ocfs2_acl_entry *entry =
(struct ocfs2_acl_entry *)value;
acl->a_entries[n].e_tag = le16_to_cpu(entry->e_tag);
acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
switch(acl->a_entries[n].e_tag) {
case ACL_USER:
acl->a_entries[n].e_uid =
make_kuid(&init_user_ns,
le32_to_cpu(entry->e_id));
break;
case ACL_GROUP:
acl->a_entries[n].e_gid =
make_kgid(&init_user_ns,
le32_to_cpu(entry->e_id));
break;
default:
break;
}
value += sizeof(struct posix_acl_entry);
}
return acl;
}
/*
* Convert acl struct to xattr value.
*/
static void *ocfs2_acl_to_xattr(const struct posix_acl *acl, size_t *size)
{
struct ocfs2_acl_entry *entry = NULL;
char *ocfs2_acl;
size_t n;
*size = acl->a_count * sizeof(struct posix_acl_entry);
ocfs2_acl = kmalloc(*size, GFP_NOFS);
if (!ocfs2_acl)
return ERR_PTR(-ENOMEM);
entry = (struct ocfs2_acl_entry *)ocfs2_acl;
for (n = 0; n < acl->a_count; n++, entry++) {
entry->e_tag = cpu_to_le16(acl->a_entries[n].e_tag);
entry->e_perm = cpu_to_le16(acl->a_entries[n].e_perm);
switch(acl->a_entries[n].e_tag) {
case ACL_USER:
entry->e_id = cpu_to_le32(
from_kuid(&init_user_ns,
acl->a_entries[n].e_uid));
break;
case ACL_GROUP:
entry->e_id = cpu_to_le32(
from_kgid(&init_user_ns,
acl->a_entries[n].e_gid));
break;
default:
entry->e_id = cpu_to_le32(ACL_UNDEFINED_ID);
break;
}
}
return ocfs2_acl;
}
static struct posix_acl *ocfs2_get_acl_nolock(struct inode *inode,
int type,
struct buffer_head *di_bh)
{
int name_index;
char *value = NULL;
struct posix_acl *acl;
int retval;
switch (type) {
case ACL_TYPE_ACCESS:
name_index = OCFS2_XATTR_INDEX_POSIX_ACL_ACCESS;
break;
case ACL_TYPE_DEFAULT:
name_index = OCFS2_XATTR_INDEX_POSIX_ACL_DEFAULT;
break;
default:
return ERR_PTR(-EINVAL);
}
retval = ocfs2_xattr_get_nolock(inode, di_bh, name_index, "", NULL, 0);
if (retval > 0) {
value = kmalloc(retval, GFP_NOFS);
if (!value)
return ERR_PTR(-ENOMEM);
retval = ocfs2_xattr_get_nolock(inode, di_bh, name_index,
"", value, retval);
}
if (retval > 0)
acl = ocfs2_acl_from_xattr(value, retval);
else if (retval == -ENODATA || retval == 0)
acl = NULL;
else
acl = ERR_PTR(retval);
kfree(value);
return acl;
}
/*
* Helper function to set i_mode in memory and disk. Some call paths
* will not have di_bh or a journal handle to pass, in which case it
* will create it's own.
*/
static int ocfs2_acl_set_mode(struct inode *inode, struct buffer_head *di_bh,
handle_t *handle, umode_t new_mode)
{
int ret, commit_handle = 0;
struct ocfs2_dinode *di;
if (di_bh == NULL) {
ret = ocfs2_read_inode_block(inode, &di_bh);
if (ret) {
mlog_errno(ret);
goto out;
}
} else
get_bh(di_bh);
if (handle == NULL) {
handle = ocfs2_start_trans(OCFS2_SB(inode->i_sb),
OCFS2_INODE_UPDATE_CREDITS);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
mlog_errno(ret);
goto out_brelse;
}
commit_handle = 1;
}
di = (struct ocfs2_dinode *)di_bh->b_data;
ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), di_bh,
OCFS2_JOURNAL_ACCESS_WRITE);
if (ret) {
mlog_errno(ret);
goto out_commit;
}
inode->i_mode = new_mode;
inode->i_ctime = current_time(inode);
di->i_mode = cpu_to_le16(inode->i_mode);
di->i_ctime = cpu_to_le64(inode->i_ctime.tv_sec);
di->i_ctime_nsec = cpu_to_le32(inode->i_ctime.tv_nsec);
ocfs2_update_inode_fsync_trans(handle, inode, 0);
ocfs2_journal_dirty(handle, di_bh);
out_commit:
if (commit_handle)
ocfs2_commit_trans(OCFS2_SB(inode->i_sb), handle);
out_brelse:
brelse(di_bh);
out:
return ret;
}
/*
* Set the access or default ACL of an inode.
*/
static int ocfs2_set_acl(handle_t *handle,
struct inode *inode,
struct buffer_head *di_bh,
int type,
struct posix_acl *acl,
struct ocfs2_alloc_context *meta_ac,
struct ocfs2_alloc_context *data_ac)
{
int name_index;
void *value = NULL;
size_t size = 0;
int ret;
if (S_ISLNK(inode->i_mode))
return -EOPNOTSUPP;
switch (type) {
case ACL_TYPE_ACCESS:
name_index = OCFS2_XATTR_INDEX_POSIX_ACL_ACCESS;
break;
case ACL_TYPE_DEFAULT:
name_index = OCFS2_XATTR_INDEX_POSIX_ACL_DEFAULT;
if (!S_ISDIR(inode->i_mode))
return acl ? -EACCES : 0;
break;
default:
return -EINVAL;
}
if (acl) {
value = ocfs2_acl_to_xattr(acl, &size);
if (IS_ERR(value))
return (int)PTR_ERR(value);
}
if (handle)
ret = ocfs2_xattr_set_handle(handle, inode, di_bh, name_index,
"", value, size, 0,
meta_ac, data_ac);
else
ret = ocfs2_xattr_set(inode, name_index, "", value, size, 0);
kfree(value);
if (!ret)
set_cached_acl(inode, type, acl);
return ret;
}
int ocfs2_iop_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
struct posix_acl *acl, int type)
{
struct buffer_head *bh = NULL;
int status, had_lock;
struct ocfs2_lock_holder oh;
struct inode *inode = d_inode(dentry);
had_lock = ocfs2_inode_lock_tracker(inode, &bh, 1, &oh);
if (had_lock < 0)
return had_lock;
if (type == ACL_TYPE_ACCESS && acl) {
umode_t mode;
status = posix_acl_update_mode(&init_user_ns, inode, &mode,
&acl);
if (status)
goto unlock;
status = ocfs2_acl_set_mode(inode, bh, NULL, mode);
if (status)
goto unlock;
}
status = ocfs2_set_acl(NULL, inode, bh, type, acl, NULL, NULL);
unlock:
ocfs2_inode_unlock_tracker(inode, 1, &oh, had_lock);
brelse(bh);
return status;
}
struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type, bool rcu)
{
struct ocfs2_super *osb;
struct buffer_head *di_bh = NULL;
struct posix_acl *acl;
int had_lock;
struct ocfs2_lock_holder oh;
if (rcu)
return ERR_PTR(-ECHILD);
osb = OCFS2_SB(inode->i_sb);
if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
return NULL;
had_lock = ocfs2_inode_lock_tracker(inode, &di_bh, 0, &oh);
if (had_lock < 0)
return ERR_PTR(had_lock);
down_read(&OCFS2_I(inode)->ip_xattr_sem);
acl = ocfs2_get_acl_nolock(inode, type, di_bh);
up_read(&OCFS2_I(inode)->ip_xattr_sem);
ocfs2_inode_unlock_tracker(inode, 0, &oh, had_lock);
brelse(di_bh);
return acl;
}
int ocfs2_acl_chmod(struct inode *inode, struct buffer_head *bh)
{
struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
struct posix_acl *acl;
int ret;
if (S_ISLNK(inode->i_mode))
return -EOPNOTSUPP;
if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
return 0;
down_read(&OCFS2_I(inode)->ip_xattr_sem);
acl = ocfs2_get_acl_nolock(inode, ACL_TYPE_ACCESS, bh);
up_read(&OCFS2_I(inode)->ip_xattr_sem);
if (IS_ERR_OR_NULL(acl))
return PTR_ERR_OR_ZERO(acl);
ret = __posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
if (ret)
return ret;
ret = ocfs2_set_acl(NULL, inode, NULL, ACL_TYPE_ACCESS,
acl, NULL, NULL);
posix_acl_release(acl);
return ret;
}
/*
* Initialize the ACLs of a new inode. If parent directory has default ACL,
* then clone to new inode. Called from ocfs2_mknod.
*/
int ocfs2_init_acl(handle_t *handle,
struct inode *inode,
struct inode *dir,
struct buffer_head *di_bh,
struct buffer_head *dir_bh,
struct ocfs2_alloc_context *meta_ac,
struct ocfs2_alloc_context *data_ac)
{
struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
struct posix_acl *acl = NULL;
int ret = 0, ret2;
umode_t mode;
if (!S_ISLNK(inode->i_mode)) {
if (osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) {
down_read(&OCFS2_I(dir)->ip_xattr_sem);
acl = ocfs2_get_acl_nolock(dir, ACL_TYPE_DEFAULT,
dir_bh);
up_read(&OCFS2_I(dir)->ip_xattr_sem);
if (IS_ERR(acl))
return PTR_ERR(acl);
}
if (!acl) {
mode = inode->i_mode & ~current_umask();
ret = ocfs2_acl_set_mode(inode, di_bh, handle, mode);
if (ret) {
mlog_errno(ret);
goto cleanup;
}
}
}
if ((osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) && acl) {
if (S_ISDIR(inode->i_mode)) {
ret = ocfs2_set_acl(handle, inode, di_bh,
ACL_TYPE_DEFAULT, acl,
meta_ac, data_ac);
if (ret)
goto cleanup;
}
mode = inode->i_mode;
ret = __posix_acl_create(&acl, GFP_NOFS, &mode);
if (ret < 0)
return ret;
ret2 = ocfs2_acl_set_mode(inode, di_bh, handle, mode);
if (ret2) {
mlog_errno(ret2);
ret = ret2;
goto cleanup;
}
if (ret > 0) {
ret = ocfs2_set_acl(handle, inode,
di_bh, ACL_TYPE_ACCESS,
acl, meta_ac, data_ac);
}
}
cleanup:
posix_acl_release(acl);
return ret;
}
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