[PATCH v2] [BZ #15855] malloc: Check for integer overflow in pvalloc.

[Will Newton]

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

ChangeLog:

2013-08-12  Will Newton  <will.newton@linaro.org>

	[BZ #15855]
	* malloc/malloc.c (__libc_pvalloc): Check the value of bytes
	does not overflow.
---
 malloc/malloc.c | 4 ++++
 1 file changed, 4 insertions(+)

Changes in v2:
 - Add BZ number

diff --git a/malloc/malloc.c b/malloc/malloc.c
index be472b2..7468758 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3082,6 +3082,10 @@ __libc_pvalloc(size_t bytes)
   size_t page_mask = GLRO(dl_pagesize) - 1;
   size_t rounded_bytes = (bytes + page_mask) & ~(page_mask);

+  /* Check for overflow.  */
+  if (bytes + 2*pagesz + MINSIZE < bytes)
+    return 0;
+
   void *(*hook) (size_t, size_t, const void *) =
     force_reg (__memalign_hook);
   if (__builtin_expect (hook != NULL, 0))
-- 
1.8.1.4