linux-kernel - Re: [PATCH] sched: fix possible divide by zero in avg

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]

Date:	Mon, 7 Jul 2014 14:44:09 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mateusz Guzik <mguzik@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	stable@...r.kernel.org
Subject: Re: [PATCH] sched: fix possible divide by zero in avg_atom
 calculation

On Sat, Jun 14, 2014 at 03:00:09PM +0200, Mateusz Guzik wrote:
> proc_sched_show_task does:
> if (nr_switches)
> 	do_div(avg_atom, nr_switches);
> 
> nr_switches is unsigned long and do_div truncates it to 32 bits, which
> means it can test non-zero on e.g. x86-64 and be truncated to zero for
> division.
> 
> Fix the problem by using div64_ul instead.
> 
> As a side effect calculations of avg_atom for big nr_switches are now correct.
> 
> Signed-off-by: Mateusz Guzik <mguzik@...hat.com>

Thanks.

Content of type "application/pgp-signature" skipped