* [PATCH AUTOSEL 4.9 84/90] ceph: fix potential race in ceph_check_caps
[not found] <20200918021455.2067301-1-sashal@kernel.org>
@ 2020-09-18 2:14 ` Sasha Levin
0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2020-09-18 2:14 UTC (permalink / raw)
To: linux-kernel, stable; +Cc: Jeff Layton, Ilya Dryomov, Sasha Levin, ceph-devel
From: Jeff Layton <jlayton@kernel.org>
[ Upstream commit dc3da0461cc4b76f2d0c5b12247fcb3b520edbbf ]
Nothing ensures that session will still be valid by the time we
dereference the pointer. Take and put a reference.
In principle, we should always be able to get a reference here, but
throw a warning if that's ever not the case.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/ceph/caps.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index e11aacb35d6b5..cbd92dd89de16 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -1807,12 +1807,24 @@ ack:
if (mutex_trylock(&session->s_mutex) == 0) {
dout("inverting session/ino locks on %p\n",
session);
+ session = ceph_get_mds_session(session);
spin_unlock(&ci->i_ceph_lock);
if (took_snap_rwsem) {
up_read(&mdsc->snap_rwsem);
took_snap_rwsem = 0;
}
- mutex_lock(&session->s_mutex);
+ if (session) {
+ mutex_lock(&session->s_mutex);
+ ceph_put_mds_session(session);
+ } else {
+ /*
+ * Because we take the reference while
+ * holding the i_ceph_lock, it should
+ * never be NULL. Throw a warning if it
+ * ever is.
+ */
+ WARN_ON_ONCE(true);
+ }
goto retry;
}
}
--
2.25.1
^ permalink raw reply related [flat|nested] only message in thread
only message in thread, other threads:[~2020-09-18 2:24 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
[not found] <20200918021455.2067301-1-sashal@kernel.org>
2020-09-18 2:14 ` [PATCH AUTOSEL 4.9 84/90] ceph: fix potential race in ceph_check_caps Sasha Levin
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).