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From: Daniel Borkmann <dborkman@redhat.com>
To: Andrey Ryabinin <a.ryabinin@samsung.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>,
	Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Michal Marek <mmarek@suse.cz>,
	Sasha Levin <sasha.levin@oracle.com>,
	x86@kernel.org, linux-kbuild@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	Dmitry Vyukov <dvyukov@google.com>,
	Konstantin Khlebnikov <koct9i@gmail.com>
Subject: Re: drivers: random: Shift out-of-bounds in _mix_pool_bytes
Date: Mon, 20 Oct 2014 16:09:30 +0200	[thread overview]
Message-ID: <5445179A.4080804@redhat.com> (raw)
In-Reply-To: <54451501.2070700@samsung.com>

On 10/20/2014 03:58 PM, Andrey Ryabinin wrote:
> On 10/20/2014 04:49 PM, Theodore Ts'o wrote:
>> On Mon, Oct 20, 2014 at 03:03:22PM +0400, Andrey Ryabinin wrote:
>>> Hi, Theodore.
>>>
>>> I've got this while booting kernel with ubsan:
>>>
>>>      [    0.000000] ================================================================================
>>>      [    0.000000] UBSan: Undefined behaviour in ../include/linux/bitops.h:107:33
>>>      [    0.000000] shift exponent 32 is to large for 32-bit type 'unsigned int'
>>        ...
>>>      [    0.000000] _mix_pool_bytes (/home/andrew/linux/ubsan_x86//include/linux/bitopsh:107 /home/andrew/linux/ubsan_x86//drivers/char/randomc:509)
>>
>> So this doesn't make any sense to me.   This is triggering here:
>>
>> 	w = rol32(*bytes++, input_rotate);
>>
>> .... but input_rotate should never be >= 32, since it is set this way:
>>
>
> It's triggering when input_rotate == 0, so UBSan complains about right shift in rol32()
>
> static inline __u32 rol32(__u32 word, unsigned int shift)
> {
> 	return (word << shift) | (word >> (32 - shift));
> }

So that would be the case when the entropy store's input_rotate calls
_mix_pool_bytes() for the very first time ... I don't think it's an
issue though.

  parent reply	other threads:[~2014-10-20 14:10 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-20 10:54 [RFC] UBSan: run-time undefined behavior sanity checker Andrey Ryabinin
2014-10-20 10:54 ` [RFC PATCH] " Andrey Ryabinin
2014-10-20 19:35   ` Sasha Levin
2014-10-21  8:03     ` Andrey Ryabinin
2014-10-24  8:31       ` y.gribov
2014-10-24 10:36         ` Andrey Ryabinin
2014-10-21  9:47   ` Peter Zijlstra
2014-10-21 10:09     ` Andrey Ryabinin
2014-10-24 10:30       ` Peter Zijlstra
2014-10-21 17:06   ` Randy Dunlap
2014-10-22  9:58   ` Rasmus Villemoes
2014-10-22 11:16     ` Andrey Ryabinin
2014-10-20 11:03 ` drivers: random: Shift out-of-bounds in _mix_pool_bytes Andrey Ryabinin
2014-10-20 12:49   ` Theodore Ts'o
2014-10-20 13:58     ` Andrey Ryabinin
2014-10-20 14:08       ` Theodore Ts'o
2014-10-20 14:09       ` Daniel Borkmann [this message]
2014-10-20 14:13         ` Sasha Levin
2014-10-20 14:16         ` Theodore Ts'o
2014-10-20 14:42           ` Andrey Ryabinin
2014-10-24 10:01           ` Peter Zijlstra
2014-10-24 10:16             ` Andrey Ryabinin
2014-10-24 13:23             ` Sasha Levin
2014-10-24 13:42               ` Peter Zijlstra
2014-10-24 15:04                 ` Sasha Levin
2014-10-24 15:10                   ` Dmitry Vyukov
2014-10-24 21:05                     ` One Thousand Gnomes
2014-10-24 22:23                       ` H. Peter Anvin
2014-10-24 22:09                     ` Andreas Dilger
2014-10-24 22:22                       ` H. Peter Anvin
2014-10-25  0:50                         ` Sasha Levin
2014-10-25 20:30                           ` One Thousand Gnomes
2014-10-25 20:49                             ` Andrey Ryabinin
2014-10-20 11:07 ` kernel: clockevents: shift out-of-bounds Andrey Ryabinin
2014-10-24 10:25   ` Peter Zijlstra
2014-10-20 11:16 ` fs: ext4: mballoc: negative shift exponent Andrey Ryabinin
2014-10-20 11:23 ` jbd2: revoke: negative shift exponent in hash() Andrey Ryabinin

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