From 27daabd9b6a157c34a6e7a7f509fa26866e6420f Mon Sep 17 00:00:00 2001
From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Mon, 8 Jul 2013 16:01:58 -0700
Subject: [PATCH] lib/scatterlist: error handling in __sg_alloc_table()

I was reviewing code which I suspected might allocate a zero size SG
table.  That will cause memory corruption.  Also we can't return before
doing the memset or we could end up using uninitialized memory in the
cleanup path.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 lib/scatterlist.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 129a82f707df..a685c8a79578 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -247,13 +247,15 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents,
 	struct scatterlist *sg, *prv;
 	unsigned int left;
 
+	memset(table, 0, sizeof(*table));
+
+	if (nents == 0)
+		return -EINVAL;
 #ifndef ARCH_HAS_SG_CHAIN
 	if (WARN_ON_ONCE(nents > max_ents))
 		return -EINVAL;
 #endif
 
-	memset(table, 0, sizeof(*table));
-
 	left = nents;
 	prv = NULL;
 	do {