ovl: fix regression caused by overlapping layers detection

Once upon a time, commit 2cac0c00a6cd ("ovl: get exclusive ownership on
upper/work dirs") in v4.13 added some sanity checks on overlayfs layers.
This change caused a docker regression. The root cause was mount leaks
by docker, which as far as I know, still exist.

To mitigate the regression, commit 85fdee1eef1a ("ovl: fix regression
caused by exclusive upper/work dir protection") in v4.14 turned the
mount errors into warnings for the default index=off configuration.

Recently, commit 146d62e5a586 ("ovl: detect overlapping layers") in
v5.2, re-introduced exclusive upper/work dir checks regardless of
index=off configuration.

This changes the status quo and mount leak related bug reports have
started to re-surface. Restore the status quo to fix the regressions.
To clarify, index=off does NOT relax overlapping layers check for this
ovelayfs mount. index=off only relaxes exclusive upper/work dir checks
with another overlayfs mount.

To cover the part of overlapping layers detection that used the
exclusive upper/work dir checks to detect overlap with self upper/work
dir, add a trap also on the work base dir.

Link: https://github.com/moby/moby/issues/34672
Link: https://lore.kernel.org/linux-fsdevel/[email protected]/
Link: https://github.com/containers/libpod/issues/3540
Fixes: 146d62e5a586 ("ovl: detect overlapping layers")
Cc: <[email protected]> # v4.19+
Signed-off-by: Amir Goldstein <[email protected]>
Tested-by: Colin Walters <[email protected]>
Signed-off-by: Miklos Szeredi <[email protected]>

0 files changed, 0 insertions, 0 deletions