linux-kernel - Re: divide error: bdi_dirty

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20120924122053.GD22303@aftab.osrc.amd.com>
Date:	Mon, 24 Sep 2012 14:20:53 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Fengguang Wu <fengguang.wu@...el.com>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Borislav Petkov <bp@...64.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <jweiner@...hat.com>,
	Conny Seidel <conny.seidel@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: divide error: bdi_dirty_limit+0x5a/0x9e

On Mon, Sep 24, 2012 at 07:34:47PM +0800, Fengguang Wu wrote:
> Will you test such a line? At least the generic do_div() only uses the
> lower 32bits for division.
> 
>         WARN_ON(!(den & 0xffffffff));

But, but, the asm output says:

  28:   48 89 c8                mov    %rcx,%rax
  2b:*  48 f7 f7                div    %rdi     <-- trapping instruction
  2e:   31 d2                   xor    %edx,%edx

and this version of DIV does an unsigned division of RDX:RAX by the
contents of a *64-bit register* ... in our case %rdi.

Srivatsa's oops  shows the same:

  28:   48 89 f0                mov    %rsi,%rax
  2b:*  48 f7 f7                div    %rdi     <-- trapping instruction
  2e:   41 8b 94 24 74 02 00    mov    0x274(%r12),%edx

Right?

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
HRB Nr. 43632 WEEE Registernr: 129 19551
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/