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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aAgO59L0ccXl6kUs@pop-os.localdomain>
Date: Tue, 22 Apr 2025 14:49:27 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
To: "Alan J. Wylie" <alan@...ie.me.uk>
Cc: Holger Hoffstätte <holger@...lied-asynchrony.com>,
	Jamal Hadi Salim <jhs@...atatu.com>, regressions@...ts.linux.dev,
	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Octavian Purdila <tavip@...gle.com>,
	Toke Høiland-Jørgensen <toke@...hat.com>,
	stable@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [REGRESSION] 6.14.3 panic - kernel NULL pointer dereference in
 htb_dequeue

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);
 }
 
 /**