netdev - [PATCH v2] net: sched: tapr: remove WARN_ON() in taprio_get_start

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Message-Id: <20210415075953.83508-2-ducheng2@gmail.com>
Date:   Thu, 15 Apr 2021 15:59:53 +0800
From:   Du Cheng <ducheng2@...il.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, Shuah Khan <skhan@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        eric.dumazet@...il.com, Du Cheng <ducheng2@...il.com>,
        syzbot+d50710fd0873a9c6b40c@...kaller.appspotmail.com
Subject: [PATCH v2] net: sched: tapr: remove WARN_ON() in taprio_get_start_time

There is a reproducible sequence from the userland that will trigger a WARN_ON()
condition in taprio_get_start_time, which causes kernel to panic if configured
as "panic_on_warn". Remove this WARN_ON() to prevent kernel from crashing by
userland-initiated syscalls.

Reported as bug on syzkaller:
https://syzkaller.appspot.com/bug?extid=d50710fd0873a9c6b40c

Reported-by: syzbot+d50710fd0873a9c6b40c@...kaller.appspotmail.com
Signed-off-by: Du Cheng <ducheng2@...il.com>
---
changelog:
v1: Discussion https://lore.kernel.org/netdev/YHfwUmFODUHx8G5W@carbon/T/
v2: fix typo


 net/sched/sch_taprio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 8287894541e3..33a829c1ba9b 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -996,7 +996,7 @@ static int taprio_get_start_time(struct Qdisc *sch,
 	 * something went really wrong. In that case, we should warn about this
 	 * inconsistent state and return error.
 	 */
-	if (WARN_ON(!cycle))
+	if (!cycle)
 		return -EFAULT;
 
 	/* Schedule the start time for the beginning of the next
-- 
2.30.2