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From: Thomas Gleixner <tglx@linutronix.de>
To: syzbot 
	<bot+d85a4a76747ecb51a02faa3009877c4ffea665d6@syzkaller.appspotmail.com>
Cc: douly.fnst@cn.fujitsu.com, hpa@zytor.com, jgross@suse.com,
	linux-kernel@vger.kernel.org, mingo@redhat.com,
	peterz@infradead.org, rostedt@goodmis.org,
	syzkaller-bugs@googlegroups.com, x86@kernel.org
Subject: Re: WARNING in rcu_process_callbacks
Date: Sat, 23 Dec 2017 20:36:35 +0100 (CET)	[thread overview]
Message-ID: <alpine.DEB.2.20.1712232031010.1853@nanos> (raw)
In-Reply-To: <94eb2c03c9bc3e1f310560ffd911@google.com>

On Sat, 23 Dec 2017, syzbot wrote:
> Hello,
> 
> syzkaller hit the following crash on 6084b576dca2e898f5c101baef151f7bfdbb606d
> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> 
> Unfortunately, I don't have any reproducer for this bug yet.
> 
> 
> RBP: 00007f50826f4a90 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000004b75bb
> R13: 00007f50826f4bc8 R14: 00000000004b75bb R15: 0000000000000000
> WARNING: CPU: 0 PID: 7719 at kernel/rcu/tree.c:2714 arch_local_irq_disable
> arch/x86/include/asm/paravirt.h:772 [inline]

So the only thing which triggers a BUG in that code is the paravirt stuff

#define PVOP_TEST_NULL(op)      BUG_ON(op == NULL)

Your config has PARAVIRT_DEBUG=y

So this is again something which got executed before a gazillion of times
and then something becomes NULL. In this case it's  pv_irq_ops.irq_disable

I've seen such unexplainable NULL pointers in quite some sysbot bug reports
lately. The irq_desc->irq_data.common issue is more or less the same
problem. This really stinks like a stray pointer.

Thanks,

	tglx

           reply	other threads:[~2017-12-23 19:37 UTC|newest]

Thread overview: expand[flat|nested]  mbox.gz  Atom feed
 [parent not found: <94eb2c03c9bc3e1f310560ffd911@google.com>]

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