From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Jeff Layton <jlayton@kernel.org>,
Ilya Dryomov <idryomov@gmail.com>,
Sasha Levin <sashal@kernel.org>,
ceph-devel@vger.kernel.org
Subject: [PATCH AUTOSEL 4.19 190/206] ceph: fix potential race in ceph_check_caps
Date: Thu, 17 Sep 2020 22:07:46 -0400 [thread overview]
Message-ID: <20200918020802.2065198-190-sashal@kernel.org> (raw)
In-Reply-To: <20200918020802.2065198-1-sashal@kernel.org>
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 a2d4eed27f804..c0dbf8b7762b4 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2015,12 +2015,24 @@ 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
prev parent reply other threads:[~2020-09-18 2:39 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200918020802.2065198-1-sashal@kernel.org>
2020-09-18 2:05 ` [PATCH AUTOSEL 4.19 062/206] ceph: ensure we have a new cap before continuing in fill_inode Sasha Levin
2020-09-18 2:07 ` Sasha Levin [this message]
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