Re: [syzbot] [net?] general protection fault in drr_qlen_notify

[syzbot <syzbot+15b96fc3aac35468fe77@syzkaller.appspotmail.com>]

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Subject: Re: [syzbot] [net?] general protection fault in drr_qlen_notify
Author: lizhi.xu@windriver.com

#syz test

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index c5e3673aadbe..c4ca8f3b820b 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -817,7 +817,8 @@ void qdisc_tree_reduce_backlog(struct Qdisc *sch, int n, int len)
 		cops = sch->ops->cl_ops;
 		if (notify && cops->qlen_notify) {
 			cl = cops->find(sch, parentid);
-			cops->qlen_notify(sch, cl);
+			if (virt_addr_valid(cl))
+				cops->qlen_notify(sch, cl);
 		}
 		sch->q.qlen -= n;
 		sch->qstats.backlog -= len;