[PATCH v3] [BZ #15857] malloc: Check for integer overflow in memalign.

[Will Newton]

A large bytes parameter to memalign could cause an integer overflow
and corrupt allocator internals. Check the overflow does not occur
before continuing with the allocation.

ChangeLog:

2013-08-16  Will Newton  <will.newton@linaro.org>

	[BZ #15857]
	* malloc/malloc.c (__libc_memalign): Check the value of bytes
	does not overflow.
---
 malloc/malloc.c | 7 +++++++
 1 file changed, 7 insertions(+)

Changes in v3:
 - Reorder if condition
 - Set errno appropriately

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 3148c5f..f7718a9 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3015,6 +3015,13 @@ __libc_memalign(size_t alignment, size_t bytes)
   /* Otherwise, ensure that it is at least a minimum chunk size */
   if (alignment <  MINSIZE) alignment = MINSIZE;

+  /* Check for overflow.  */
+  if (bytes > SIZE_MAX - alignment - MINSIZE)
+    {
+      __set_errno (ENOMEM);
+      return 0;
+    }
+
   arena_get(ar_ptr, bytes + alignment + MINSIZE);
   if(!ar_ptr)
     return 0;
-- 
1.8.1.4