[v3,BZ,#15855] malloc: Check for integer overflow in pvalloc.

Message ID 522F1BA2.9070301@linaro.org
State Accepted
Headers show

Commit Message

Will Newton Sept. 10, 2013, 1:16 p.m.
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 | 7 +++++++
 1 file changed, 7 insertions(+)

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

Comments

Siddhesh Poyarekar Sept. 10, 2013, 1:35 p.m. | #1
On 10 September 2013 18:46, Will Newton <will.newton@linaro.org> wrote:
> +  /* Check for overflow.  */
> +  if (bytes > SIZE_MAX - 2*pagesz - MINSIZE)

Spaces between operator and operands.  Looks OK to me with that change.

Siddhesh

> +    {
> +      __set_errno (ENOMEM);
> +      return 0;
> +    }
> +
>    void *(*hook) (size_t, size_t, const void *) =
>      force_reg (__memalign_hook);
>    if (__builtin_expect (hook != NULL, 0))
> --
> 1.8.1.4
>

Patch

diff --git a/malloc/malloc.c b/malloc/malloc.c
index dd295f5..7f43ba3 100644
--- 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))