Re: [REGRESSION] 6.14.3 panic - kernel NULL pointer dereference in htb_dequeue

[Cong Wang <xiyou.wangcong@gmail.com>]

Hi, Alan

Although I am still trying to understand the NULL pointer, which seems
likely from:

 478                         if (p->inner.clprio[prio].ptr == cl->node + prio) {
 479                                 /* we are removing child which is pointed to from
 480                                  * parent feed - forget the pointer but remember
 481                                  * classid
 482                                  */
 483                                 p->inner.clprio[prio].last_ptr_id = cl->common.classid;
 484                                 p->inner.clprio[prio].ptr = NULL;
 485                         }

Does the following patch work? I mean not just fixing the crash, but
also not causing any other problem.

Please give it a try.

Thanks!

---

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 4b9a639b642e..0cdc778fddef 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -348,7 +348,8 @@ static void htb_add_to_wait_tree(struct htb_sched *q,
  */
 static inline void htb_next_rb_node(struct rb_node **n)
 {
-	*n = rb_next(*n);
+	if (*n)
+		*n = rb_next(*n);
 }
 
 /**