This is a note to let you know that I've just added the patch titled

ovl: force r/o mount when index dir creation fails

to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: ovl-force-r-o-mount-when-index-dir-creation-fails.patch and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 972d0093c2f7b1bd57e47a1780a552dde528fd16 Mon Sep 17 00:00:00 2001

From: Amir Goldstein amir73il@gmail.com Date: Tue, 19 Sep 2017 12:14:18 +0300 Subject: ovl: force r/o mount when index dir creation fails

From: Amir Goldstein amir73il@gmail.com

commit 972d0093c2f7b1bd57e47a1780a552dde528fd16 upstream.

When work dir creation fails, a warning is emitted and overlay is mounted r/o. Trying to remount r/w will fail with no work dir.

When index dir creation fails, the same warning is emitted and overlay is mounted r/o, but trying to remount r/w will succeed. This may cause unintentional corruption of filesystem consistency.

Adjust the behavior of index dir creation failure to that of work dir creation failure and do not allow to remount r/w. User needs to state an explicitly intention to work without an index by mounting with option 'index=off' to allow r/w mount with no index dir.

When mounting with option 'index=on' and no 'upperdir', index is implicitly disabled, so do not warn about no file handle support.

The issue was introduced with inodes index feature in v4.13, but this patch will not apply cleanly before ovl_fill_super() re-factoring in v4.15.

Fixes: 02bcd1577400 ("ovl: introduce the inodes index dir feature") Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- fs/overlayfs/super.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)

--- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -703,7 +703,8 @@ static int ovl_lower_dir(const char *nam * The inodes index feature needs to encode and decode file * handles, so it requires that all layers support them. */ - if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) { + if (ofs->config.index && ofs->config.upperdir && + !ovl_can_decode_fh(path->dentry->d_sb)) { ofs->config.index = false; pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name); } @@ -1257,11 +1258,16 @@ static int ovl_fill_super(struct super_b if (err) goto out_free_oe;

- if (!ofs->indexdir) + /* Force r/o mount with no index dir */ + if (!ofs->indexdir) { + dput(ofs->workdir); + ofs->workdir = NULL; sb->s_flags |= SB_RDONLY; + } + }

- /* Show index=off/on in /proc/mounts for any of the reasons above */ + /* Show index=off in /proc/mounts for forced r/o mount */ if (!ofs->indexdir) ofs->config.index = false;

Patches currently in stable-queue which might be from amir73il@gmail.com are

queue-4.15/ovl-take-mnt_want_write-for-removing-impure-xattr.patch queue-4.15/ovl-take-mnt_want_write-for-work-index-dir-setup.patch queue-4.15/ovl-hash-directory-inodes-for-fsnotify.patch queue-4.15/ovl-force-r-o-mount-when-index-dir-creation-fails.patch queue-4.15/ovl-fix-failure-to-fsync-lower-dir.patch