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authorMiklos Szeredi <mszeredi@suse.cz>2011-07-15 14:49:21 +0200
committerJohn Rigby <john.rigby@linaro.org>2011-11-16 14:25:03 -0700
commit64c9efed874cf221fb117a45d7a2461d886c5f38 (patch)
tree4970a9dade02d4676fbe0c83397d8856d6e7c74f /fs
parent66fe77a3bc5bde2919c30c03e49cefcfc511ec67 (diff)
downloadlinux-linaro-precise-64c9efed874cf221fb117a45d7a2461d886c5f38.tar.gz
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>
Diffstat (limited to 'fs')
-rw-r--r--fs/ecryptfs/main.c7
-rw-r--r--fs/overlayfs/super.c10
2 files changed, 17 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)) {