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From:   Kees Cook <keescook@chromium.org>
Date:   Fri, 6 Apr 2018 11:02:46 -0700
Message-ID: <CAGXu5jKLsdfHEySg1w5EKO3Tt3=nWh7txWVsU6V65i3vS=Z2xw@mail.gmail.com>
Subject: Re: [bisected] 3c8ba0d61d04ced9f8d9ff93977995a9e4e96e91 oopses on s390
To:     Sebastian Ott <sebott@linux.vnet.ibm.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Martin Uecker <Martin.Uecker@med.uni-goettingen.de>,
        Ingo Molnar <mingo@kernel.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
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On Fri, Apr 6, 2018 at 9:47 AM, Kees Cook <keescook@chromium.org> wrote:
> On Fri, Apr 6, 2018 at 2:47 AM, Sebastian Ott <sebott@linux.vnet.ibm.com> wrote:
>> Today's kernel oopsed on s390. Bisect points to:
>> 3c8ba0d61d04 ("kernel.h: Retain constant expression output for max()/min()")
>>
>> [    1.898277] dasd-eckd 0.0.3304: DASD with 4 KB/block, 21636720 KB total size, 48 KB/track, compatible disk layout
>> [    1.898308] ------------[ cut here ]------------
>> [    1.898310] kernel BUG at block/bio.c:1798!
>
> Well that's extremely bad. :(
>
>> Bisect log and config attached. I'll look at min/max users in the affected
>> areas later today.
>
> Seems like a comparison of objdump output with/without the patch may
> be needed. And why is this s390 only? Ugh.

I did a objdump diff with your .config and it's rather large -- mostly
seems to be register swaps, so it's not easy to browse.

BTW, what version of gcc did you use? I built using:

s390x-linux-gnu-gcc (Ubuntu 7.3.0-13ubuntu1) 7.3.0

-Kees

-- 
Kees Cook
Pixel Security