From: Xiubo Li <xiubli@xxxxxxxxxx> commit 7acae6183cf37c48b8da48bbbdb78820fb3913f3 upstream. 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@xxxxxxxxxxxxxxx URL: https://tracker.ceph.com/issues/55327 Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> Tested-by: Aaron Tomlin <atomlin@xxxxxxxxxx> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ceph/caps.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -2266,6 +2266,8 @@ 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++) { @@ -2286,6 +2288,8 @@ 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++) {
