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SubjectRe: [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 <>

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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