ceph: fix potential race in ceph_check_caps (dc3da046) · Commits · 戴 / test

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>

fs/ceph/caps.c

+13 −1

Original line number	Diff line number	Diff line
		@@ -2044,12 +2044,24 @@ 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;
		}
		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;
		}
		}

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