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From: Andrey Ryabinin <ryabinin.a.a@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>,
	Ingo Molnar <mingo@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: perf/ring-buffer: Undefined behaviour in kernel/events/ring_buffer.c:685:22
Date: Fri, 22 Jan 2016 15:48:55 +0300	[thread overview]
Message-ID: <CAPAsAGyWy0OqB6+NMfeAyNeGLV8oS9MmKQ=GGNiVwAO6VdkP5g@mail.gmail.com> (raw)
In-Reply-To: <20160119143111.GH6344@twins.programming.kicks-ass.net>

2016-01-19 17:31 GMT+03:00 Peter Zijlstra <peterz@infradead.org>:
> On Sun, Jan 10, 2016 at 03:55:13PM -0500, Sasha Levin wrote:
>> Hi all,
>>
>> While fuzzing with trinity inside a KVM tools guest, running the latest -next
>> kernel, I've hit the following warning:
>>
>> [ 3494.030114] UBSAN: Undefined behaviour in kernel/events/ring_buffer.c:685:22
>> [ 3494.030647] shift exponent -1 is negative
>
> That's rb->page_order == -1, which should 'never' happen, curious!
>

It happens if nr_pages = 0:
     rb->page_order = ilog2(nr_pages);

  parent reply	other threads:[~2016-01-22 12:49 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-10 20:55 Sasha Levin
2016-01-19 14:31 ` Peter Zijlstra
2016-01-21 23:34   ` Sasha Levin
2016-01-22 12:48   ` Andrey Ryabinin [this message]
2016-01-29 14:17     ` Peter Zijlstra
2016-03-21  9:51       ` [tip:perf/urgent] perf/core: Fix Undefined behaviour in rb_alloc() tip-bot for Peter Zijlstra

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