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From: Dmitry Vyukov <dvyukov@google.com>
To: Johannes Berg <johannes@sipsolutions.net>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Hillf Danton <hdanton@sina.com>,
	syzbot <syzbot+27df43cf7ae73de7d8ee@syzkaller.appspotmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: BUG: soft lockup in ieee80211_tasklet_handler
Date: Tue, 2 Mar 2021 20:01:34 +0100	[thread overview]
Message-ID: <CACT4Y+ahrV-L8vV8Jm8XP=KwjWivFj445GULY1fbRN9t7buMGw@mail.gmail.com> (raw)
In-Reply-To: <0a0573f07a7e1468f83d52afcf8f5ba356725740.camel@sipsolutions.net>

On Tue, Mar 2, 2021 at 3:18 PM Johannes Berg <johannes@sipsolutions.net> wrote:
>
> On Wed, 2021-02-24 at 10:30 +0800, Hillf Danton wrote:
> >
> > Add budget for the 80211 softint handler - it's feasible not to try to
> > build the giant pyramid in a week.
> >
> > --- x/net/mac80211/main.c
> > +++ y/net/mac80211/main.c
> > @@ -224,9 +224,15 @@ static void ieee80211_tasklet_handler(un
> >  {
> >       struct ieee80211_local *local = (struct ieee80211_local *) data;
> >       struct sk_buff *skb;
> > +     int i = 0;
> > +
> > +     while (i++ < 64) {
> > +             skb = skb_dequeue(&local->skb_queue);
> > +             if (!skb)
> > +                     skb = skb_dequeue(&local->skb_queue_unreliable);
> > +             if (!skb)
> > +                     return;
>
> I guess that's not such a bad idea, but I do wonder how we get here,
> userspace can submit packets faster than we can process?
>
> It feels like a simulation-only case, tbh, since over the air you have
> limits how much bandwidth you can get ... unless you have a very slow
> CPU?
>
> In any case, if you want anything merged you're going to have to submit
> a proper patch with a real commit message and Signed-off-by, etc.

Looking at the reproducer that mostly contains just perf_event_open,
It may be the old known issue of perf_event_open with some extreme
parameters bringing down kernel.
+perf maintainers
And as far as I remember +Peter had some patch to restrict
perf_event_open parameters.

r0 = perf_event_open(&(0x7f000001d000)={0x1, 0x70, 0x0, 0x0, 0x0, 0x0,
0x0, 0x3ff, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xfffffffe, 0x0, @perf_config_ext}, 0x0,
0x0, 0xffffffffffffffff, 0x0)

  reply	other threads:[~2021-03-02 22:08 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-23 17:55 BUG: soft lockup in ieee80211_tasklet_handler syzbot
2021-03-02  8:10 ` syzbot
     [not found] ` <20210224023026.3001-1-hdanton@sina.com>
2021-03-02 14:18   ` Johannes Berg
2021-03-02 19:01     ` Dmitry Vyukov [this message]
2021-03-04  8:30       ` Johannes Berg
     [not found]     ` <20210303085912.1647-1-hdanton@sina.com>
2021-03-03  9:06       ` Dmitry Vyukov

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