diff options
| author | Miklos Szeredi <mszeredi@suse.cz> | 2011-07-15 14:49:21 +0200 |
|---|---|---|
| committer | John Rigby <john.rigby@linaro.org> | 2011-10-17 09:52:18 -0600 |
| commit | fef83af9b28738e1d21b25ee1a07bf74862092e5 (patch) | |
| tree | 9d5bea073ffc5d37855607cc31b20ca60c128ff8 | |
| parent | 1d256f62f8ac5c20cee8818c07353598669768c5 (diff) | |
UBUNTU: ubuntu: overlayfs -- fs: limit filesystem stacking depth
Add a simple read-only counter to super_block that indicates deep this
is in the stack of filesystems. Previously ecryptfs was the only
stackable filesystem and it explicitly disallowed multiple layers of
itself.
Overlayfs, however, can be stacked recursively and also may be stacked
on top of ecryptfs or vice versa.
To limit the kernel stack usage we must limit the depth of the
filesystem stack. Initially the limit is set to 2.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
| -rw-r--r-- | fs/ecryptfs/main.c | 7 | ||||
| -rw-r--r-- | fs/overlayfs/super.c | 10 | ||||
| -rw-r--r-- | include/linux/fs.h | 11 |
3 files changed, 28 insertions, 0 deletions
diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c index b4a6befb121..703cda3bb66 100644 --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -544,6 +544,13 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags s->s_maxbytes = path.dentry->d_sb->s_maxbytes; s->s_blocksize = path.dentry->d_sb->s_blocksize; s->s_magic = ECRYPTFS_SUPER_MAGIC; + s->s_stack_depth = path.dentry->d_sb->s_stack_depth + 1; + + rc = -EINVAL; + if (s->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { + printk(KERN_ERR "eCryptfs: maximum fs stacking depth exceeded\n"); + goto out_free; + } inode = ecryptfs_get_inode(path.dentry->d_inode, s); rc = PTR_ERR(inode); diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 427bb555020..a64f0f4820e 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -545,6 +545,16 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) !S_ISDIR(lowerpath.dentry->d_inode->i_mode)) goto out_put_lowerpath; + sb->s_stack_depth = max(upperpath.mnt->mnt_sb->s_stack_depth, + lowerpath.mnt->mnt_sb->s_stack_depth) + 1; + + err = -EINVAL; + if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) { + printk(KERN_ERR "overlayfs: maximum fs stacking depth exceeded\n"); + goto out_put_lowerpath; + } + + ufs->upper_mnt = clone_private_mount(&upperpath); err = PTR_ERR(ufs->upper_mnt); if (IS_ERR(ufs->upper_mnt)) { diff --git a/include/linux/fs.h b/include/linux/fs.h index b43dee4fe69..ab7d83bdf75 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -480,6 +480,12 @@ struct iattr { */ #include <linux/quota.h> +/* + * Maximum number of layers of fs stack. Needs to be limited to + * prevent kernel stack overflow + */ +#define FILESYSTEM_MAX_STACK_DEPTH 2 + /** * enum positive_aop_returns - aop return codes with specific semantics * @@ -1438,6 +1444,11 @@ struct super_block { * Saved pool identifier for cleancache (-1 means none) */ int cleancache_poolid; + + /* + * Indicates how deep in a filesystem stack this SB is + */ + int s_stack_depth; }; extern struct timespec current_fs_time(struct super_block *sb); |