From: Hillf Danton <hdanton@sina.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: syzbot <syzbot+d1ae9c954f73570e7b58@syzkaller.appspotmail.com>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
syzkaller-bugs@googlegroups.com,
Johannes Berg <johannes.berg@intel.com>,
Kalle Valo <kvalo@codeaurora.org>,
linux-wireless@vger.kernel.org
Subject: Re: [syzbot] [kernel?] WARNING in hrtimer_forward (2)
Date: Wed, 10 Apr 2024 06:51:39 +0800 [thread overview]
Message-ID: <20240409225139.1556-1-hdanton@sina.com> (raw)
In-Reply-To: <87a5m27r08.ffs@tglx>
On Tue, 09 Apr 2024 12:46:31 +0200 Thomas Gleixner <tglx@linutronix.de>
> On Mon, Apr 08 2024 at 19:46, syzbot wrote:
> > ------------[ cut here ]------------
> > WARNING: CPU: 1 PID: 11239 at kernel/time/hrtimer.c:1053 hrtimer_forward+0x210/0x2d0 kernel/time/hrtimer.c:1053
> > RIP: 0010:hrtimer_forward+0x210/0x2d0 kernel/time/hrtimer.c:1053
> > Call Trace:
> > <IRQ>
> > hrtimer_forward_now include/linux/hrtimer.h:355 [inline]
> > mac80211_hwsim_beacon+0x192/0x1f0 drivers/net/wireless/virtual/mac80211_hwsim.c:2335
> > __run_hrtimer kernel/time/hrtimer.c:1692 [inline]
> > __hrtimer_run_queues+0x595/0xd00 kernel/time/hrtimer.c:1756
> > hrtimer_run_softirq+0x19a/0x2c0 kernel/time/hrtimer.c:1773
> > __do_softirq+0x2bc/0x943 kernel/softirq.c:554
> > invoke_softirq kernel/softirq.c:428 [inline]
> > __irq_exit_rcu+0xf2/0x1c0 kernel/softirq.c:633
> > irq_exit_rcu+0x9/0x30 kernel/softirq.c:645
> > instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
> > sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1043
> > </IRQ>
>
> The code which arms the timer is not serialized against the callback so
> the following can happen:
>
> CPU1 CPU2
>
> __run_hrtimer(timer)
> if (!hrtimer_queued(timer))
> hrtimer_start(timer);
>
> hrtimer_forward(timer)
> WARN_ON(hrtimer_queued(timer)
>
> This really wants to use hrtimer_active() which takes the running
> callback into account.
>
Then the race window is still open with hrtimer_active() and serialization
outside hrtimer is needed.
CPU1 CPU2
--- ---
if (!hrtimer_is_active(timer))
if (!hrtimer_is_active(timer))
hrtimer_start(timer);
__run_hrtimer(timer)
hrtimer_start(timer);
hrtimer_forward(timer)
WARN_ON(hrtimer_queued(timer))
prev parent reply other threads:[~2024-04-09 22:52 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-09 2:46 syzbot
2024-04-09 10:46 ` Thomas Gleixner
2024-04-09 22:51 ` Hillf Danton [this message]
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