ovl: get exclusive ownership on upper/work dirs
authorAmir Goldstein <amir73il@gmail.com>
Wed, 21 Jun 2017 12:28:33 +0000 (15:28 +0300)
committerMiklos Szeredi <mszeredi@redhat.com>
Tue, 4 Jul 2017 20:03:17 +0000 (22:03 +0200)
commit2cac0c00a6cdcc9121de150ed531f652396d1544
tree2c0d163277aad85c8226ed385735fc4f40bde939
parentad0af7104dadccd55cd2b390271677fac142650f
ovl: get exclusive ownership on upper/work dirs

Bad things can happen if several concurrent overlay mounts try to
use the same upperdir/workdir path.

Try to get the 'inuse' advisory lock on upperdir and workdir.
Fail mount if another overlay mount instance or another user
holds the 'inuse' lock on these directories.

Note that this provides no protection for concurrent overlay
mount that use overlapping (i.e. descendant) upper/work dirs.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
fs/overlayfs/ovl_entry.h
fs/overlayfs/super.c