nfsd: fix use-after-free due to delegation race
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1991929
Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=42523663
commit 548ec0805c399c65ed66c6641be467f717833ab5
Author: J. Bruce Fields bfields@redhat.com
Date: Mon Nov 29 15:08:00 2021 -0500
nfsd: fix use-after-free due to delegation race
A delegation break could arrive as soon as we've called vfs_setlease. A
delegation break runs a callback which immediately (in
nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we
then exit nfs4_set_delegation without hashing the delegation, it will be
freed as soon as the callback is done with it, without ever being
removed from del_recall_lru.
Symptoms show up later as use-after-free or list corruption warnings,
usually in the laundromat thread.
I suspect aba2072f4523 "nfsd: grant read delegations to clients holding
writes" made this bug easier to hit, but I looked as far back as v3.0
and it looks to me it already had the same problem. So I'm not sure
where the bug was introduced; it may have been there from the beginning.
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Benjamin Coddington bcodding@redhat.com