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***

Subject: [syzbot] [kernel?] general protection fault in put_ipc_ns
Author: hellouser819@gmail.com

#syz test
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 535f16e..ea3015c 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -201,7 +201,7 @@ static void free_ipc(struct work_struct *unused)
  */
 void put_ipc_ns(struct ipc_namespace *ns)
 {
-       if (ns_ref_put_and_lock(ns, &mq_lock)) {
+       if (ns != NULL && ns_ref_put_and_lock(ns, &mq_lock)) {
                mq_clear_sbinfo(ns);
                spin_unlock(&mq_lock);