linux-kernel - Re: [PATCH -tip/cpus4096-v2] cpumask: fix cpumask of call_function

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Message-Id: <200810281146.28491.rusty@rustcorp.com.au>
Date:	Tue, 28 Oct 2008 11:46:26 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH -tip/cpus4096-v2] cpumask: fix cpumask of	call_function_data

On Tuesday 28 October 2008 10:07:26 Hiroshi Shimamoto wrote:
> So, kmalloc(8, flags) for cpumask_var_t at alloc_cpumask_var().
> But the content is treated as cpumask_t, it causes slab corruption
> with overwritten when the mask data is copied.

Yes.  This is another one.

Ingo, please fold.

Subject: Fix slab corruption when using CONFIG_CPUMASK_OFFSTACK

Found by Hiroshi Shimamoto; using assignment on a cpumask_t causes slab
corruption, as we do not allocate sizeof(struct cpumask).

It looks like we will have to stick with allocating all NR_CPUS bits until the
end of the patchset (in the future) where we have eliminated all the
cpumask_t assignments.

(Note: this ban will be enforced by compiler when we get rid of the 'struct
cpumask' definition, which is what we're slowly working towards).

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index d1f22ee..004da56 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -182,7 +182,8 @@ int cpumask_any_but(const struct cpumask *mask, unsigned int cpu);
 
 static inline size_t cpumask_size(void)
 {
-	return BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long);
+	/* FIXME: Use nr_cpumask_bits once all cpumask_t assignments banished */
+	return BITS_TO_LONGS(NR_CPUS) * sizeof(long);
 }
 
 /* Deprecated. */

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