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

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>

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 31204cd..5c14ef0 100644 (file)
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2274,6 +2274,8 @@ 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++) {
@@ -2294,6 +2296,8 @@ 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++) {