From: pageexec@freemail.hu
To: Andrew Morton <akpm@linux-foundation.org>,
Andi Kleen <ak@suse.de>,
travis@sgi.com
Cc: Christoph Lameter <clameter@sgi.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] mm: Prevent dereferencing non-allocated per_cpu variables
Date: Wed, 28 Nov 2007 00:01:57 +0200 [thread overview]
Message-ID: <474CAFF5.8792.356C2F62@pageexec.freemail.hu> (raw)
In-Reply-To: <20071127215054.660250000@sgi.com>
On 27 Nov 2007 at 13:50, travis@sgi.com wrote:
> Change loops controlled by 'for (i = 0; i < NR_CPUS; i++)' to use
> 'for_each_possible_cpu(i)' when there's a _remote possibility_ of
> dereferencing a non-allocated per_cpu variable involved.
actually, it's not that remote, it happens every time
NR_CPUS > num_possible_cpus(). i ran into this myself
on a dual core box with NR_CPUS=4. due to my rewrite
of the i386 per-cpu segment handling, i actually got
a NULL deref where the vanilla kernel would be accessing
the area of [__per_cpu_start, __per_cpu_end] for each
non-possible CPU (which doesn't crash per se but is
still not correct somehow i think).
WARNING: multiple messages have this Message-ID (diff)
From: pageexec@freemail.hu
To: Andrew Morton <akpm@linux-foundation.org>,
Andi Kleen <ak@suse.de>,
travis@sgi.com
Cc: Christoph Lameter <clameter@sgi.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] mm: Prevent dereferencing non-allocated per_cpu variables
Date: Wed, 28 Nov 2007 00:01:57 +0200 [thread overview]
Message-ID: <474CAFF5.8792.356C2F62@pageexec.freemail.hu> (raw)
In-Reply-To: <20071127215054.660250000@sgi.com>
On 27 Nov 2007 at 13:50, travis@sgi.com wrote:
> Change loops controlled by 'for (i = 0; i < NR_CPUS; i++)' to use
> 'for_each_possible_cpu(i)' when there's a _remote possibility_ of
> dereferencing a non-allocated per_cpu variable involved.
actually, it's not that remote, it happens every time
NR_CPUS > num_possible_cpus(). i ran into this myself
on a dual core box with NR_CPUS=4. due to my rewrite
of the i386 per-cpu segment handling, i actually got
a NULL deref where the vanilla kernel would be accessing
the area of [__per_cpu_start, __per_cpu_end] for each
non-possible CPU (which doesn't crash per se but is
still not correct somehow i think).
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next prev parent reply other threads:[~2007-11-27 23:02 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20071127215052.090968000@sgi.com>
2007-11-27 21:50 ` [PATCH 1/1] mm: Prevent dereferencing non-allocated per_cpu variables travis
2007-11-27 21:50 ` travis
2007-11-27 22:01 ` pageexec [this message]
2007-11-27 22:01 ` pageexec
2007-11-27 22:16 ` Andi Kleen
2007-11-27 22:16 ` Andi Kleen
2007-11-27 23:12 ` Andrew Morton
2007-11-27 23:12 ` Andrew Morton
2007-11-27 23:15 ` Christoph Lameter
2007-11-27 23:15 ` Christoph Lameter
2007-11-27 23:21 ` Andrew Morton
2007-11-27 23:21 ` Andrew Morton
2007-11-27 23:22 ` Christoph Lameter
2007-11-27 23:22 ` Christoph Lameter
2007-11-27 23:42 ` Andrew Morton
2007-11-27 23:42 ` Andrew Morton
2007-11-27 23:48 ` Andi Kleen
2007-11-27 23:48 ` Andi Kleen
2007-11-28 0:15 ` Christoph Lameter
2007-11-28 0:15 ` Christoph Lameter
2007-11-28 0:09 ` Christoph Lameter
2007-11-28 0:09 ` Christoph Lameter
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