ceph: fix possible NULL pointer dereference for req->r_session

[ Upstream commit 7acae6183cf37c48b8da48bbbdb78820fb3913f3 ]

The request will be inserted into the ci->i_unsafe_dirops before
assigning the req->r_session, so it's possible that we will hit
NULL pointer dereference bug here.

Cc: stable@vger.kernel.org
URL: https://tracker.ceph.com/issues/55327
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Stable-dep-of: 5bd76b8de5b7 ("ceph: fix NULL pointer dereference for req->r_session")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 4e2fada358080a7abaa9486483a3e61ccc112829..ce6a858e765ab57327a34914ecc5cc9629794bfb 100644 (file)
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2346,6 +2346,8 @@ retry:
                        list_for_each_entry(req, &ci->i_unsafe_dirops,
                                            r_unsafe_dir_item) {
                                s = req->r_session;
+                               if (!s)
+                                       continue;
                                if (unlikely(s->s_mds >= max_sessions)) {
                                        spin_unlock(&ci->i_unsafe_lock);
                                        for (i = 0; i < max_sessions; i++) {
@@ -2366,6 +2368,8 @@ retry:
                        list_for_each_entry(req, &ci->i_unsafe_iops,
                                            r_unsafe_target_item) {
                                s = req->r_session;
+                               if (!s)
+                                       continue;
                                if (unlikely(s->s_mds >= max_sessions)) {
                                        spin_unlock(&ci->i_unsafe_lock);
                                        for (i = 0; i < max_sessions; i++) {