Hi Miklos,
Vincent reported[1] what appears to be a regression in Overlayfs with
4.0. This was found in the upstream docker community[2] on Ubuntu
with 4.0.1 as well, so it is distro agnostic. The following sequence
of commands in the bug report seems to allow one to remove a non-empty
directory.
Is this expected behavior now? I looked through the commits in 4.0
and saw a few that might lead to a behavior change, but I am not
familiar enough with Overalyfs to know if this was intentional or not.
josh
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1220915
[2] https://github.com/docker/docker/issues/13108
On Wed, May 13, 2015 at 09:06:26AM -0400, Josh Boyer wrote:
> Hi Miklos,
>
> Vincent reported[1] what appears to be a regression in Overlayfs with
> 4.0. This was found in the upstream docker community[2] on Ubuntu
> with 4.0.1 as well, so it is distro agnostic. The following sequence
> of commands in the bug report seems to allow one to remove a non-empty
> directory.
>
> Is this expected behavior now? I looked through the commits in 4.0
> and saw a few that might lead to a behavior change, but I am not
> familiar enough with Overalyfs to know if this was intentional or not.
>
> josh
>
> [1] https://bugzilla.redhat.com/show_bug.cgi?id=1220915
> [2] https://github.com/docker/docker/issues/13108
Good report, thanks!
Follwing patch should fix it.
Thanks,
Miklos
---
Subject: ovl: don't remove non-empty opaque directory
From: Miklos Szeredi <[email protected]>
When removing an opaque directory we can't just call rmdir() to check for
emptyness, because the directory will need to be replaced with a whiteout.
The replacement is done with RENAME_EXCHANGE, which doesn't check
emptyness.
Solution is just to check emptyness by reading the directory. In the
future we could add a new rename flag to check for emptyness even for
RENAME_EXCHANGE to optimize this case.
Reported-by: Vincent Batts <[email protected]>
Signed-off-by: Miklos Szeredi <[email protected]>
Fixes: 263b4a0fee43 ("ovl: dont replace opaque dir")
Cc: <[email protected]> # v4.0+
---
fs/overlayfs/dir.c | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -506,11 +506,25 @@ static int ovl_remove_and_whiteout(struc
struct dentry *opaquedir = NULL;
int err;
- if (is_dir && OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
- opaquedir = ovl_check_empty_and_clear(dentry);
- err = PTR_ERR(opaquedir);
- if (IS_ERR(opaquedir))
- goto out;
+ if (is_dir) {
+ if (OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
+ opaquedir = ovl_check_empty_and_clear(dentry);
+ err = PTR_ERR(opaquedir);
+ if (IS_ERR(opaquedir))
+ goto out;
+ } else {
+ LIST_HEAD(list);
+
+ /*
+ * When removing an empty opaque directory, then it
+ * makes no sense to replace it with an exact replica of
+ * itself. But emptiness still needs to be checked.
+ */
+ err = ovl_check_empty_dir(dentry, &list);
+ ovl_cache_free(&list);
+ if (err)
+ goto out;
+ }
}
err = ovl_lock_rename_workdir(workdir, upperdir);
Hello,
Tested-by: Jordi Pujol Palomer <[email protected]>
Have compiled the version 4.0.3 adding this patch, it works in a
Live OS,
# rmdir /mnt/
# mkdir -p /mnt
# touch /mnt/file
# rmdir /mnt/
rmdir: failed to remove ‘/mnt/’: Directory not empty
# uname -a
Linux pcjordi 4.0.3-1-haswell-lnet-amd64 #1 SMP PREEMPT Wed May 13 19:38:19 CEST 2015 x86_64 GNU/Linux
#
Thanks,
Jordi Pujol
EL Wed, 13 May 2015 17:11:01 +0200
Miklos Szeredi <[email protected]> escrigué:
> ---
> Subject: ovl: don't remove non-empty opaque directory
> From: Miklos Szeredi <[email protected]>
>
> When removing an opaque directory we can't just call rmdir() to check
> for emptyness, because the directory will need to be replaced with a
> whiteout. The replacement is done with RENAME_EXCHANGE, which doesn't
> check emptyness.
>
> Solution is just to check emptyness by reading the directory. In the
> future we could add a new rename flag to check for emptyness even for
> RENAME_EXCHANGE to optimize this case.
>
> Reported-by: Vincent Batts <[email protected]>
> Signed-off-by: Miklos Szeredi <[email protected]>
> Fixes: 263b4a0fee43 ("ovl: dont replace opaque dir")
> Cc: <[email protected]> # v4.0+
> ---