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| author | Miklos Szeredi <mszeredi@suse.cz> | 2014-10-24 00:14:39 +0200 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@suse.cz> | 2014-10-24 00:14:39 +0200 |
| commit | 69c433ed2ecd2d3264efd7afec4439524b319121 (patch) | |
| tree | 49fcf55fbd3913881ccb47a6e700f668a4307daf /fs | |
| parent | overlay: overlay filesystem documentation (diff) | |
| download | linux-69c433ed2ecd2d3264efd7afec4439524b319121.tar.xz linux-69c433ed2ecd2d3264efd7afec4439524b319121.zip | |
fs: limit filesystem stacking depth
Add a simple read-only counter to super_block that indicates how 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>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/ecryptfs/main.c | 7 | ||||
| -rw-r--r-- | fs/overlayfs/super.c | 9 |
2 files changed, 16 insertions, 0 deletions
diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c index 1b119d3bf924..c4cd1fd86cc2 100644 --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -566,6 +566,13 @@ 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) { + pr_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 7dcc24e84417..08b704cebfc4 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -677,6 +677,15 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) } ufs->lower_namelen = statfs.f_namelen; + 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) { + pr_err("overlayfs: maximum fs stacking depth exceeded\n"); + goto out_put_workpath; + } + ufs->upper_mnt = clone_private_mount(&upperpath); err = PTR_ERR(ufs->upper_mnt); if (IS_ERR(ufs->upper_mnt)) { |