malloc: Check for integer overflow in pvalloc.

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:

2013-09-11  Will Newton  <will.newton@linaro.org>

	[BZ #15855]
	* malloc/malloc.c (__libc_pvalloc): Check the value of bytes
	does not overflow.

(cherry picked from commit 7e0e64ead52591b968df582b0ddc247ba5c4eab4)

diff --git a/malloc/malloc.c b/malloc/malloc.c
index be472b2ba3885b194f55c29474c4ad5d6a61b729..bcc08c45f7bf759933fa2ccf8a7fbce2be03d7be 100644 (file)
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3082,6 +3082,13 @@ __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 > SIZE_MAX - 2*pagesz - MINSIZE)
+    {
+      __set_errno (ENOMEM);
+      return 0;
+    }
+
   void *(*hook) (size_t, size_t, const void *) =
     force_reg (__memalign_hook);
   if (__builtin_expect (hook != NULL, 0))