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linux/fs/bfs/inode.c
Eric W. Biederman 7f78e03513 fs: Limit sys_mount to only request filesystem modules. 
Modify the request_module to prefix the file system type with "fs-"
and add aliases to all of the filesystems that can be built as modules
to match.

A common practice is to build all of the kernel code and leave code
that is not commonly needed as modules, with the result that many
users are exposed to any bug anywhere in the kernel.

Looking for filesystems with a fs- prefix limits the pool of possible
modules that can be loaded by mount to just filesystems trivially
making things safer with no real cost.

Using aliases means user space can control the policy of which
filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf
with blacklist and alias directives.  Allowing simple, safe,
well understood work-arounds to known problematic software.

This also addresses a rare but unfortunate problem where the filesystem
name is not the same as it's module name and module auto-loading
would not work.  While writing this patch I saw a handful of such
cases.  The most significant being autofs that lives in the module
autofs4.

This is relevant to user namespaces because we can reach the request
module in get_fs_type() without having any special permissions, and
people get uncomfortable when a user specified string (in this case
the filesystem type) goes all of the way to request_module.

After having looked at this issue I don't think there is any
particular reason to perform any filtering or permission checks beyond
making it clear in the module request that we want a filesystem
module.  The common pattern in the kernel is to call request_module()
without regards to the users permissions.  In general all a filesystem
module does once loaded is call register_filesystem() and go to sleep.
Which means there is not much attack surface exposed by loading a
filesytem module unless the filesystem is mounted.  In a user
namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT,
which most filesystems do not set today.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reported-by: Kees Cook <keescook@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2013-03-03 19:36:31 -08:00

501 lines
12 KiB
C
Raw Blame History

/*
* fs/bfs/inode.c
* BFS superblock and inode operations.
* Copyright (C) 1999-2006 Tigran Aivazian <tigran@aivazian.fsnet.co.uk>
* From fs/minix, Copyright (C) 1991, 1992 Linus Torvalds.
*
* Made endianness-clean by Andrew Stribblehill <ads@wompom.org>, 2005.
*/
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/vfs.h>
#include <linux/writeback.h>
#include <asm/uaccess.h>
#include "bfs.h"
MODULE_AUTHOR("Tigran Aivazian <tigran@aivazian.fsnet.co.uk>");
MODULE_DESCRIPTION("SCO UnixWare BFS filesystem for Linux");
MODULE_LICENSE("GPL");
#undef DEBUG
#ifdef DEBUG
#define dprintf(x...) printf(x)
#else
#define dprintf(x...)
#endif
void dump_imap(const char *prefix, struct super_block *s);
struct inode *bfs_iget(struct super_block *sb, unsigned long ino)
{
struct bfs_inode *di;
struct inode *inode;
struct buffer_head *bh;
int block, off;
inode = iget_locked(sb, ino);
if (IS_ERR(inode))
return ERR_PTR(-ENOMEM);
if (!(inode->i_state & I_NEW))
return inode;
if ((ino < BFS_ROOT_INO) || (ino > BFS_SB(inode->i_sb)->si_lasti)) {
printf("Bad inode number %s:%08lx\n", inode->i_sb->s_id, ino);
goto error;
}
block = (ino - BFS_ROOT_INO) / BFS_INODES_PER_BLOCK + 1;
bh = sb_bread(inode->i_sb, block);
if (!bh) {
printf("Unable to read inode %s:%08lx\n", inode->i_sb->s_id,
ino);
goto error;
}
off = (ino - BFS_ROOT_INO) % BFS_INODES_PER_BLOCK;
di = (struct bfs_inode *)bh->b_data + off;
inode->i_mode = 0x0000FFFF & le32_to_cpu(di->i_mode);
if (le32_to_cpu(di->i_vtype) == BFS_VDIR) {
inode->i_mode |= S_IFDIR;
inode->i_op = &bfs_dir_inops;
inode->i_fop = &bfs_dir_operations;
} else if (le32_to_cpu(di->i_vtype) == BFS_VREG) {
inode->i_mode |= S_IFREG;
inode->i_op = &bfs_file_inops;
inode->i_fop = &bfs_file_operations;
inode->i_mapping->a_ops = &bfs_aops;
}
BFS_I(inode)->i_sblock = le32_to_cpu(di->i_sblock);
BFS_I(inode)->i_eblock = le32_to_cpu(di->i_eblock);
BFS_I(inode)->i_dsk_ino = le16_to_cpu(di->i_ino);
i_uid_write(inode, le32_to_cpu(di->i_uid));
i_gid_write(inode, le32_to_cpu(di->i_gid));
set_nlink(inode, le32_to_cpu(di->i_nlink));
inode->i_size = BFS_FILESIZE(di);
inode->i_blocks = BFS_FILEBLOCKS(di);
inode->i_atime.tv_sec = le32_to_cpu(di->i_atime);
inode->i_mtime.tv_sec = le32_to_cpu(di->i_mtime);
inode->i_ctime.tv_sec = le32_to_cpu(di->i_ctime);
inode->i_atime.tv_nsec = 0;
inode->i_mtime.tv_nsec = 0;
inode->i_ctime.tv_nsec = 0;
brelse(bh);
unlock_new_inode(inode);
return inode;
error:
iget_failed(inode);
return ERR_PTR(-EIO);
}
static struct bfs_inode *find_inode(struct super_block *sb, u16 ino, struct buffer_head **p)
{
if ((ino < BFS_ROOT_INO) || (ino > BFS_SB(sb)->si_lasti)) {
printf("Bad inode number %s:%08x\n", sb->s_id, ino);
return ERR_PTR(-EIO);
}
ino -= BFS_ROOT_INO;
*p = sb_bread(sb, 1 + ino / BFS_INODES_PER_BLOCK);
if (!*p) {
printf("Unable to read inode %s:%08x\n", sb->s_id, ino);
return ERR_PTR(-EIO);
}
return (struct bfs_inode *)(*p)->b_data + ino % BFS_INODES_PER_BLOCK;
}
static int bfs_write_inode(struct inode *inode, struct writeback_control *wbc)
{
struct bfs_sb_info *info = BFS_SB(inode->i_sb);
unsigned int ino = (u16)inode->i_ino;
unsigned long i_sblock;
struct bfs_inode *di;
struct buffer_head *bh;
int err = 0;
dprintf("ino=%08x\n", ino);
di = find_inode(inode->i_sb, ino, &bh);
if (IS_ERR(di))
return PTR_ERR(di);
mutex_lock(&info->bfs_lock);
if (ino == BFS_ROOT_INO)
di->i_vtype = cpu_to_le32(BFS_VDIR);
else
di->i_vtype = cpu_to_le32(BFS_VREG);
di->i_ino = cpu_to_le16(ino);
di->i_mode = cpu_to_le32(inode->i_mode);
di->i_uid = cpu_to_le32(i_uid_read(inode));
di->i_gid = cpu_to_le32(i_gid_read(inode));
di->i_nlink = cpu_to_le32(inode->i_nlink);
di->i_atime = cpu_to_le32(inode->i_atime.tv_sec);
di->i_mtime = cpu_to_le32(inode->i_mtime.tv_sec);
di->i_ctime = cpu_to_le32(inode->i_ctime.tv_sec);
i_sblock = BFS_I(inode)->i_sblock;
di->i_sblock = cpu_to_le32(i_sblock);
di->i_eblock = cpu_to_le32(BFS_I(inode)->i_eblock);
di->i_eoffset = cpu_to_le32(i_sblock * BFS_BSIZE + inode->i_size - 1);
mark_buffer_dirty(bh);
if (wbc->sync_mode == WB_SYNC_ALL) {
sync_dirty_buffer(bh);
if (buffer_req(bh) && !buffer_uptodate(bh))
err = -EIO;
}
brelse(bh);
mutex_unlock(&info->bfs_lock);
return err;
}
static void bfs_evict_inode(struct inode *inode)
{
unsigned long ino = inode->i_ino;
struct bfs_inode *di;
struct buffer_head *bh;
struct super_block *s = inode->i_sb;
struct bfs_sb_info *info = BFS_SB(s);
struct bfs_inode_info *bi = BFS_I(inode);
dprintf("ino=%08lx\n", ino);
truncate_inode_pages(&inode->i_data, 0);
invalidate_inode_buffers(inode);
clear_inode(inode);
if (inode->i_nlink)
return;
di = find_inode(s, inode->i_ino, &bh);
if (IS_ERR(di))
return;
mutex_lock(&info->bfs_lock);
/* clear on-disk inode */
memset(di, 0, sizeof(struct bfs_inode));
mark_buffer_dirty(bh);
brelse(bh);
if (bi->i_dsk_ino) {
if (bi->i_sblock)
info->si_freeb += bi->i_eblock + 1 - bi->i_sblock;
info->si_freei++;
clear_bit(ino, info->si_imap);
dump_imap("delete_inode", s);
}
/*
* If this was the last file, make the previous block
* "last block of the last file" even if there is no
* real file there, saves us 1 gap.
*/
if (info->si_lf_eblk == bi->i_eblock)
info->si_lf_eblk = bi->i_sblock - 1;
mutex_unlock(&info->bfs_lock);
}
static void bfs_put_super(struct super_block *s)
{
struct bfs_sb_info *info = BFS_SB(s);
if (!info)
return;
mutex_destroy(&info->bfs_lock);
kfree(info->si_imap);
kfree(info);
s->s_fs_info = NULL;
}
static int bfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
struct super_block *s = dentry->d_sb;
struct bfs_sb_info *info = BFS_SB(s);
u64 id = huge_encode_dev(s->s_bdev->bd_dev);
buf->f_type = BFS_MAGIC;
buf->f_bsize = s->s_blocksize;
buf->f_blocks = info->si_blocks;
buf->f_bfree = buf->f_bavail = info->si_freeb;
buf->f_files = info->si_lasti + 1 - BFS_ROOT_INO;
buf->f_ffree = info->si_freei;
buf->f_fsid.val[0] = (u32)id;
buf->f_fsid.val[1] = (u32)(id >> 32);
buf->f_namelen = BFS_NAMELEN;
return 0;
}
static struct kmem_cache *bfs_inode_cachep;
static struct inode *bfs_alloc_inode(struct super_block *sb)
{
struct bfs_inode_info *bi;
bi = kmem_cache_alloc(bfs_inode_cachep, GFP_KERNEL);
if (!bi)
return NULL;
return &bi->vfs_inode;
}
static void bfs_i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
kmem_cache_free(bfs_inode_cachep, BFS_I(inode));
}
static void bfs_destroy_inode(struct inode *inode)
{
call_rcu(&inode->i_rcu, bfs_i_callback);
}
static void init_once(void *foo)
{
struct bfs_inode_info *bi = foo;
inode_init_once(&bi->vfs_inode);
}
static int init_inodecache(void)
{
bfs_inode_cachep = kmem_cache_create("bfs_inode_cache",
sizeof(struct bfs_inode_info),
0, (SLAB_RECLAIM_ACCOUNT|
SLAB_MEM_SPREAD),
init_once);
if (bfs_inode_cachep == NULL)
return -ENOMEM;
return 0;
}
static void destroy_inodecache(void)
{
/*
* Make sure all delayed rcu free inodes are flushed before we
* destroy cache.
*/
rcu_barrier();
kmem_cache_destroy(bfs_inode_cachep);
}
static const struct super_operations bfs_sops = {
.alloc_inode = bfs_alloc_inode,
.destroy_inode = bfs_destroy_inode,
.write_inode = bfs_write_inode,
.evict_inode = bfs_evict_inode,
.put_super = bfs_put_super,
.statfs = bfs_statfs,
};
void dump_imap(const char *prefix, struct super_block *s)
{
#ifdef DEBUG
int i;
char *tmpbuf = (char *)get_zeroed_page(GFP_KERNEL);
if (!tmpbuf)
return;
for (i = BFS_SB(s)->si_lasti; i >= 0; i--) {
if (i > PAGE_SIZE - 100) break;
if (test_bit(i, BFS_SB(s)->si_imap))
strcat(tmpbuf, "1");
else
strcat(tmpbuf, "0");
}
printf("BFS-fs: %s: lasti=%08lx <%s>\n",
prefix, BFS_SB(s)->si_lasti, tmpbuf);
free_page((unsigned long)tmpbuf);
#endif
}
static int bfs_fill_super(struct super_block *s, void *data, int silent)
{
struct buffer_head *bh, *sbh;
struct bfs_super_block *bfs_sb;
struct inode *inode;
unsigned i, imap_len;
struct bfs_sb_info *info;
int ret = -EINVAL;
unsigned long i_sblock, i_eblock, i_eoff, s_size;
info = kzalloc(sizeof(*info), GFP_KERNEL);
if (!info)
return -ENOMEM;
mutex_init(&info->bfs_lock);
s->s_fs_info = info;
sb_set_blocksize(s, BFS_BSIZE);
sbh = sb_bread(s, 0);
if (!sbh)
goto out;
bfs_sb = (struct bfs_super_block *)sbh->b_data;
if (le32_to_cpu(bfs_sb->s_magic) != BFS_MAGIC) {
if (!silent)
printf("No BFS filesystem on %s (magic=%08x)\n",
s->s_id, le32_to_cpu(bfs_sb->s_magic));
goto out1;
}
if (BFS_UNCLEAN(bfs_sb, s) && !silent)
printf("%s is unclean, continuing\n", s->s_id);
s->s_magic = BFS_MAGIC;
if (le32_to_cpu(bfs_sb->s_start) > le32_to_cpu(bfs_sb->s_end)) {
printf("Superblock is corrupted\n");
goto out1;
}
info->si_lasti = (le32_to_cpu(bfs_sb->s_start) - BFS_BSIZE) /
sizeof(struct bfs_inode)
+ BFS_ROOT_INO - 1;
imap_len = (info->si_lasti / 8) + 1;
info->si_imap = kzalloc(imap_len, GFP_KERNEL);
if (!info->si_imap)
goto out1;
for (i = 0; i < BFS_ROOT_INO; i++)
set_bit(i, info->si_imap);
s->s_op = &bfs_sops;
inode = bfs_iget(s, BFS_ROOT_INO);
if (IS_ERR(inode)) {
ret = PTR_ERR(inode);
goto out2;
}
s->s_root = d_make_root(inode);
if (!s->s_root) {
ret = -ENOMEM;
goto out2;
}
info->si_blocks = (le32_to_cpu(bfs_sb->s_end) + 1) >> BFS_BSIZE_BITS;
info->si_freeb = (le32_to_cpu(bfs_sb->s_end) + 1
- le32_to_cpu(bfs_sb->s_start)) >> BFS_BSIZE_BITS;
info->si_freei = 0;
info->si_lf_eblk = 0;
/* can we read the last block? */
bh = sb_bread(s, info->si_blocks - 1);
if (!bh) {
printf("Last block not available: %lu\n", info->si_blocks - 1);
ret = -EIO;
goto out3;
}
brelse(bh);
bh = NULL;
for (i = BFS_ROOT_INO; i <= info->si_lasti; i++) {
struct bfs_inode *di;
int block = (i - BFS_ROOT_INO) / BFS_INODES_PER_BLOCK + 1;
int off = (i - BFS_ROOT_INO) % BFS_INODES_PER_BLOCK;
unsigned long eblock;
if (!off) {
brelse(bh);
bh = sb_bread(s, block);
}
if (!bh)
continue;
di = (struct bfs_inode *)bh->b_data + off;
/* test if filesystem is not corrupted */
i_eoff = le32_to_cpu(di->i_eoffset);
i_sblock = le32_to_cpu(di->i_sblock);
i_eblock = le32_to_cpu(di->i_eblock);
s_size = le32_to_cpu(bfs_sb->s_end);
if (i_sblock > info->si_blocks ||
i_eblock > info->si_blocks ||
i_sblock > i_eblock ||
i_eoff > s_size ||
i_sblock * BFS_BSIZE > i_eoff) {
printf("Inode 0x%08x corrupted\n", i);
brelse(bh);
ret = -EIO;
goto out3;
}
if (!di->i_ino) {
info->si_freei++;
continue;
}
set_bit(i, info->si_imap);
info->si_freeb -= BFS_FILEBLOCKS(di);
eblock = le32_to_cpu(di->i_eblock);
if (eblock > info->si_lf_eblk)
info->si_lf_eblk = eblock;
}
brelse(bh);
brelse(sbh);
dump_imap("read_super", s);
return 0;
out3:
dput(s->s_root);
s->s_root = NULL;
out2:
kfree(info->si_imap);
out1:
brelse(sbh);
out:
mutex_destroy(&info->bfs_lock);
kfree(info);
s->s_fs_info = NULL;
return ret;
}
static struct dentry *bfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_bdev(fs_type, flags, dev_name, data, bfs_fill_super);
}
static struct file_system_type bfs_fs_type = {
.owner = THIS_MODULE,
.name = "bfs",
.mount = bfs_mount,
.kill_sb = kill_block_super,
.fs_flags = FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("bfs");
static int __init init_bfs_fs(void)
{
int err = init_inodecache();
if (err)
goto out1;
err = register_filesystem(&bfs_fs_type);
if (err)
goto out;
return 0;
out:
destroy_inodecache();
out1:
return err;
}
static void __exit exit_bfs_fs(void)
{
unregister_filesystem(&bfs_fs_type);
destroy_inodecache();
}
module_init(init_bfs_fs)
module_exit(exit_bfs_fs)
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