From 70efabd0adbdaf582307593d03d2e1d5de3b4e2e Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Mon, 7 Jan 2019 16:13:48 -0600
Subject: [PATCH] mm/mm_heap/mm_calloc.c:  Verify that the number of elements
 times the size of an element will not overflow type size_t.  This is required
 by the SEI CERT C coding style and resolves anonymous Bitbucket Issue #139

---
 TODO                   |  3 +++
 mm/mm_heap/mm_calloc.c | 13 ++++++++++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/TODO b/TODO
index fbc6a089ba..3a0e8b341b 100644
--- a/TODO
+++ b/TODO
@@ -2181,6 +2181,9 @@ o File system / Generic drivers (fs/, drivers/)
                space at the seek position.  Seeking beyond the end of the file
                has the side effect of extending the file.
 
+               [NOTE: This automatic extension of the file cluster allocation
+                is probably unnecessary and another issue of its own.]
+
                For example, suppose you have a cluster size that is 4096 bytes
                and a file that is 8192 bytes long.  Then the file will consist
                of 2 allocated clusters at offsets 0 through 8191.
diff --git a/mm/mm_heap/mm_calloc.c b/mm/mm_heap/mm_calloc.c
index 43d06e2e31..56cba4bbf4 100644
--- a/mm/mm_heap/mm_calloc.c
+++ b/mm/mm_heap/mm_calloc.c
@@ -57,9 +57,20 @@ FAR void *mm_calloc(FAR struct mm_heap_s *heap, size_t n, size_t elem_size)
 {
   FAR void *ret = NULL;
 
+  /* Verify input parameters */
+
   if (n > 0 && elem_size > 0)
     {
-      ret = mm_zalloc(heap, n * elem_size);
+      /* Assure that the following multiplication cannot overflow the size_t
+       * type, i.e., that:  SIZE_MAX >= n * elem_size
+       *
+       * Refer to SEI CERT C Coding Standard.
+       */
+
+      if (n <= (SIZE_MAX / elem_size))
+        {
+          ret = mm_zalloc(heap, n * elem_size);
+        }
     }
 
   return ret;