Check for integer overflow in cache size computation in strcoll

strcoll is implemented using a cache for indices and weights of
collation sequences in the strings so that subsequent passes do not
have to search through collation data again.  For very large string
inputs, the cache size computation could overflow.  In such a case,
use the fallback function that does not cache indices and weights of
collation sequences.

Fixes CVE-2012-4412.

1 files changed, 9 insertions, 1 deletions

diff --git a/string/strcoll_l.c b/string/strcoll_l.c
index eb042ff..4ee101a 100644
--- a/string/strcoll_l.c
+++ b/string/strcoll_l.c
@@ -524,7 +524,15 @@ STRCOLL (const STRING_TYPE *s1, const STRING_TYPE *s2, __locale_t l)
   memset (&seq1, 0, sizeof (seq1));
   seq2 = seq1;
 
-  if (! __libc_use_alloca ((s1len + s2len) * (sizeof (int32_t) + 1)))
+  size_t size_max = SIZE_MAX / (sizeof (int32_t) + 1);
+
+  if (MIN (s1len, s2len) > size_max
+      || MAX (s1len, s2len) > size_max - MIN (s1len, s2len))
+    {
+      /* If the strings are long enough to cause overflow in the size request,
+         then skip the allocation and proceed with the non-cached routines.  */
+    }
+  else if (! __libc_use_alloca ((s1len + s2len) * (sizeof (int32_t) + 1)))
     {
       seq1.idxarr = (int32_t *) malloc ((s1len + s2len) * (sizeof (int32_t) + 1));