cpumask: fix slab corruption caused by alloc_cpumask_var_node()
Fix slab corruption caused by alloc_cpumask_var_node() overwriting the
tail end of an off-stack cpumask.
The function zeros out cpumask bits beyond the last possible cpu. The
starting point for zeroing should be the beginning of the mask offset by a
byte count derived from the number of possible cpus. The offset was
calculated in bits instead of bytes. This resulted in overwriting the end
of the cpumask.
Signed-off-by: Jack Steiner <steiner@sgi.com>
Acked-by: Mike Travis <travis.sgi.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: <stable@kernel.org> [2.6.29.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/cpumask.c b/lib/cpumask.c
index 3389e24..1f71b97 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -109,10 +109,10 @@
#endif
/* FIXME: Bandaid to save us from old primitives which go to NR_CPUS. */
if (*mask) {
+ unsigned char *ptr = (unsigned char *)cpumask_bits(*mask);
unsigned int tail;
tail = BITS_TO_LONGS(NR_CPUS - nr_cpumask_bits) * sizeof(long);
- memset(cpumask_bits(*mask) + cpumask_size() - tail,
- 0, tail);
+ memset(ptr + cpumask_size() - tail, 0, tail);
}
return *mask != NULL;