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: <20120925085707.GB30042@marah.osrc.amd.com>
Date:	Tue, 25 Sep 2012 10:57:09 +0200
From:	Conny Seidel <conny.seidel@....com>
To:	Jan Kara <jack@...e.cz>
CC:	Borislav Petkov <bp@...64.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Conny Seidel <conny.seidel@....com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <jweiner@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: divide error: bdi_dirty_limit+0x5a/0x9e

* Jan Kara <jack@...e.cz>:
>  [...]

The patch works for me. Tested it a couple of times on several machines
without triggering the issue.

Thanks for the fix.

> From 1fd707552a67adf869958e479910d2f70452351b Mon Sep 17 00:00:00 2001
> From: Jan Kara <jack@...e.cz>
> Date: Mon, 24 Sep 2012 16:17:16 +0200
> Subject: [PATCH] lib: Fix corruption of denominator in flexible proportions
>
> When racing with CPU hotplug, percpu_counter_sum() can return negative
> values for the number of observed events. This confuses fprop_new_period(),
> which uses unsigned type and as a result number of events is set to big
> *positive* number. From that moment on, things go pear shaped and can result
> e.g. in division by zero as denominator is later truncated to 32-bits.
>
> Fix the issue by using a signed type in fprop_new_period(). That makes us
> bail out from the function without doing anything (mistakenly) thinking
> there are no events to age. That makes aging somewhat inaccurate but getting
> accurate data would be rather hard.
>
> Reported-by: Borislav Petkov <bp@...64.org>
> Reported-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> Signed-off-by: Jan Kara <jack@...e.cz>
Tested-by: Conny Seidel <conny.seidel@....com>
> ---
>  lib/flex_proportions.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/lib/flex_proportions.c b/lib/flex_proportions.c
> index c785554..ebf3bac 100644
> --- a/lib/flex_proportions.c
> +++ b/lib/flex_proportions.c
> @@ -62,7 +62,7 @@ void fprop_global_destroy(struct fprop_global *p)
>   */
>  bool fprop_new_period(struct fprop_global *p, int periods)
>  {
> -	u64 events;
> +	s64 events;
>  	unsigned long flags;
>
>  	local_irq_save(flags);
> --
> 1.7.1
>


--
Kind regards.

Conny Seidel

##################################################################
# Email : conny.seidel@....com            GnuPG-Key : 0xA6AB055D #
# Fingerprint: 17C4 5DB2 7C4C C1C7 1452 8148 F139 7C09 A6AB 055D #
##################################################################
# Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach      #
# General Managers: Alberto Bozzo                                #
# Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen #
#               HRB Nr. 43632                                    #
##################################################################

--
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/