From: Andrey Ryabinin <a.ryabinin@samsung.com>
To: "Theodore Ts'o" <tytso@mit.edu>
Cc: 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 17:58:25 +0400 [thread overview]
Message-ID: <54451501.2070700@samsung.com> (raw)
In-Reply-To: <20141020124929.GA23177@thunk.org>
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));
}
> input_rotate = (input_rotate + (i ? 7 : 14)) & 31;
>
> Just to be sure I've tried adding a:
>
> WARN_ON(input_rotate >= 32);
>
> before the rol32 line, and it's not triggering for me after booting
> under kvm using an i386 kernel.
>
> Is this something you can reliably reproduce? Can you try putting a
> WARN_ON before the rol32() on a kernel w/o usbsan, just to make sure
> this isn't some kind of false positive? And then can you tell me
> something more about the .config you are using to build your test kernel?
>
> Thanks,
>
> - Ted
>
next prev parent reply other threads:[~2014-10-20 13:58 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 [this message]
2014-10-20 14:08 ` Theodore Ts'o
2014-10-20 14:09 ` Daniel Borkmann
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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