[PATCH v4] net: sched: tapr: prevent cycle_time == 0 in parse_taprio_schedule

[PATCH v4] net: sched: tapr: prevent cycle_time == 0 in parse_taprio_schedule

[Du Cheng]

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>
---
changelog
v1: Discussion https://lore.kernel.org/netdev/YHfwUmFODUHx8G5W@carbon/T/

v2: fix typo https://lore.kernel.org/netdev/20210415075953.83508-2-ducheng2@gmail.com/T/

v3: catch the condition in parse_taprio_schedule instead
https://lore.kernel.org/netdev/CAM_iQpWs3Z55=y0-=PJT6xZMv+Hw9JGPLFXmbr+35+70DAYsOQ@mail.gmail.com/T/

v4: add extack

 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 8287894541e3..909c798b7403 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -901,6 +901,12 @@ 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

Re: [PATCH v4] net: sched: tapr: prevent cycle_time == 0 in parse_taprio_schedule

[Cong Wang]

On Fri, Apr 16, 2021 at 4:30 PM Du Cheng <ducheng2@gmail.com> wrote:
>
> 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>

Thanks.

Re: [PATCH v4] net: sched: tapr: prevent cycle_time == 0 in parse_taprio_schedule

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Sat, 17 Apr 2021 07:30:46 +0800 you wrote:
> 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
> 
> [...]

Here is the summary with links:
  - [v4] net: sched: tapr: prevent cycle_time == 0 in parse_taprio_schedule
    https://git.kernel.org/netdev/net/c/ed8157f1ebf1

You are awesome, thank you!
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