From 0be0bfd2de9dfdd2098a9c5b14bdd8f739c9165d Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Fri, 12 Jul 2019 15:24:34 +0300 Subject: 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/20171006121405.GA32700@veci.piliscsaba.szeredi.hu/ Link: https://github.com/containers/libpod/issues/3540 Fixes: 146d62e5a586 ("ovl: detect overlapping layers") Cc: # v4.19+ Signed-off-by: Amir Goldstein Tested-by: Colin Walters Signed-off-by: Miklos Szeredi --- Documentation/filesystems/overlayfs.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'Documentation') diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt index 1da2f1668f08..845d689e0fd7 100644 --- a/Documentation/filesystems/overlayfs.txt +++ b/Documentation/filesystems/overlayfs.txt @@ -302,7 +302,7 @@ beneath or above the path of another overlay lower layer path. Using an upper layer path and/or a workdir path that are already used by another overlay mount is not allowed and may fail with EBUSY. Using -partially overlapping paths is not allowed but will not fail with EBUSY. +partially overlapping paths is not allowed and may fail with EBUSY. If files are accessed from two overlayfs mounts which share or overlap the upper layer and/or workdir path the behavior of the overlay is undefined, though it will not result in a crash or deadlock. -- cgit v1.2.3-59-g8ed1b