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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+d50710fd0873a9c6b40c@syzkaller.appspotmail.com,
        Du Cheng <ducheng2@gmail.com>,
        Cong Wang <cong.wang@bytedance.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 039/141] net: sched: tapr: prevent cycle_time == 0 in parse_taprio_schedule
Date:   Mon, 17 May 2021 16:01:31 +0200
Message-Id: <20210517140244.090269965@linuxfoundation.org>
In-Reply-To: <20210517140242.729269392@linuxfoundation.org>
References: <20210517140242.729269392@linuxfoundation.org>
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From: Du Cheng <ducheng2@gmail.com>

[ Upstream commit ed8157f1ebf1ae81a8fa2653e3f20d2076fad1c9 ]

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". Catch this condition in parse_taprio_schedule to
prevent this condition.

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

Reported-by: syzbot+d50710fd0873a9c6b40c@syzkaller.appspotmail.com
Signed-off-by: Du Cheng <ducheng2@gmail.com>
Acked-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/sched/sch_taprio.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 09116be99511..a4de4853c79d 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -900,6 +900,12 @@ static int parse_taprio_schedule(struct taprio_sched *q, struct nlattr **tb,
 
 		list_for_each_entry(entry, &new->entries, list)
 			cycle = ktime_add_ns(cycle, entry->interval);
+
+		if (!cycle) {
+			NL_SET_ERR_MSG(extack, "'cycle_time' can never be 0");
+			return -EINVAL;
+		}
+
 		new->cycle_time = cycle;
 	}
 
-- 
2.30.2