malloc: Fix for infinite loop in memalign/posix_memalign.

A very large alignment argument passed to mealign/posix_memalign
causes _int_memalign to enter an infinite loop. Limit the maximum
alignment value to the maximum representable power of two to
prevent this from happening.

Changelog:

2013-10-30  Will Newton  <will.newton@linaro.org>

	[BZ #16038]
	* malloc/hooks.c (memalign_check): Limit alignment to the
	maximum representable power of two.
	* malloc/malloc.c (__libc_memalign): Likewise.
	* malloc/tst-memalign.c (do_test): Add test for very
	large alignment values.
	* malloc/tst-posix_memalign.c (do_test): Likewise.

4 files changed, 41 insertions, 0 deletions

diff --git a/malloc/hooks.c b/malloc/hooks.c
index 3f663bb6b2..1dbe93f383 100644
--- a/malloc/hooks.c
+++ b/malloc/hooks.c
@@ -361,6 +361,14 @@ memalign_check(size_t alignment, size_t bytes, const void *caller)
   if (alignment <= MALLOC_ALIGNMENT) return malloc_check(bytes, NULL);
   if (alignment <  MINSIZE) alignment = MINSIZE;
 
+  /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a
+     power of 2 and will cause overflow in the check below.  */
+  if (alignment > SIZE_MAX / 2 + 1)
+    {
+      __set_errno (EINVAL);
+      return 0;
+    }
+
   /* Check for overflow.  */
   if (bytes > SIZE_MAX - alignment - MINSIZE)
     {
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 79025b16d9..29796fe461 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3016,6 +3016,14 @@ __libc_memalign(size_t alignment, size_t bytes)
   /* Otherwise, ensure that it is at least a minimum chunk size */
   if (alignment <  MINSIZE) alignment = MINSIZE;
 
+  /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a
+     power of 2 and will cause overflow in the check below.  */
+  if (alignment > SIZE_MAX / 2 + 1)
+    {
+      __set_errno (EINVAL);
+      return 0;
+    }
+
   /* Check for overflow.  */
   if (bytes > SIZE_MAX - alignment - MINSIZE)
     {
diff --git a/malloc/tst-memalign.c b/malloc/tst-memalign.c
index 1c59752483..cf48e7ed1f 100644
--- a/malloc/tst-memalign.c
+++ b/malloc/tst-memalign.c
@@ -70,6 +70,21 @@ do_test (void)
 
   free (p);
 
+  errno = 0;
+
+  /* Test to expose integer overflow in malloc internals from BZ #16038.  */
+  p = memalign (-1, pagesize);
+
+  save = errno;
+
+  if (p != NULL)
+    merror ("memalign (-1, pagesize) succeeded.");
+
+  if (p == NULL && save != EINVAL)
+    merror ("memalign (-1, pagesize) errno is not set correctly");
+
+  free (p);
+
   /* A zero-sized allocation should succeed with glibc, returning a
      non-NULL value.  */
   p = memalign (sizeof (void *), 0);
diff --git a/malloc/tst-posix_memalign.c b/malloc/tst-posix_memalign.c
index 27c0dd2bd4..7f34e37bd2 100644
--- a/malloc/tst-posix_memalign.c
+++ b/malloc/tst-posix_memalign.c
@@ -65,6 +65,16 @@ do_test (void)
 
   p = NULL;
 
+  /* Test to expose integer overflow in malloc internals from BZ #16038.  */
+  ret = posix_memalign (&p, -1, pagesize);
+
+  if (ret != EINVAL)
+    merror ("posix_memalign (&p, -1, pagesize) succeeded.");
+
+  free (p);
+
+  p = NULL;
+
   /* A zero-sized allocation should succeed with glibc, returning zero
      and setting p to a non-NULL value.  */
   ret = posix_memalign (&p, sizeof (void *), 0);