netdev - Re: [syzbot] [wireless?] WARNING: net/mac80211/tx.c:LINE at __ieee80211_beacon

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Message-ID: <49456d11ed8d4ff3adc71286b17dc657a6db131b.camel@sipsolutions.net>
Date: Tue, 17 Jun 2025 11:50:32 +0200
From: Johannes Berg <johannes@...solutions.net>
To: Aleksandr Nogikh <nogikh@...gle.com>
Cc: syzbot <syzbot+468656785707b0e995df@...kaller.appspotmail.com>, 
	linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org, 
	netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [wireless?] WARNING: net/mac80211/tx.c:LINE at
 __ieee80211_beacon_get, CPU: syz.NUM.NUM/NUM

On Tue, 2025-06-17 at 11:48 +0200, Aleksandr Nogikh wrote:
> On Tue, Jun 17, 2025 at 11:43 AM Johannes Berg
> <johannes@...solutions.net> wrote:
> > 
> > On Tue, 2025-06-17 at 11:34 +0200, Aleksandr Nogikh wrote:
> > > #syz dup: WARNING in __ieee80211_beacon_get
> > > 
> > 
> > Not just this one :)
> > 
> > https://lore.kernel.org/linux-wireless/20250617104902.146e10919be1.I85f352ca4a2dce6f556e5ff45ceaa5f3769cb5ce@changeid/
> > 
> 
> Ah, interesting :)
> 
> FWIW, in this particular case, syzbot sent the duplicate report
> because the WARNING format has somewhat changed in the latest
> linux-next. So before we updated syzbot's parsing rules, it had
> managed to re-report quite a few duplicates.

Right, I had noticed that, but then I looked and the old counter is
already at well over 100k so I decided to finally look at it again ;-)

This is a really long-standing problem that we discussed a few times in
the past I think, and basically the system is loaded enough that the
hwsim hrtimer can fire on time and pull the beacon, but the workqueues
are overloaded and cannot do the necessary work within the ~100ms beacon
interval ...

Should be rare in practice, but a WARN_ON() that doesn't say anything
about what's going on doesn't help anyway.

johannes