From: Jack Steiner <steiner@sgi.com>
Date: Fri, 3 Apr 2009 04:35:02 +0000 (+0000)
Subject: cpumask: fix slab corruption caused by alloc_cpumask_var_node()
X-Git-Tag: v2.6.29.2~72
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=14e4f36b873affb350f9608dfd77ce793f545fd4;p=thirdparty%2Fkernel%2Fstable.git

cpumask: fix slab corruption caused by alloc_cpumask_var_node()

upstream commit: 4f032ac4122a77dbabf7a24b2739b2790448180f

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>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---

diff --git a/lib/cpumask.c b/lib/cpumask.c
index 3389e2440da0f..1f71b97de0f94 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -109,10 +109,10 @@ bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
 #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;