Update.

2004-09-08  Ulrich Drepper  <drepper@redhat.com>

	* malloc/malloc.c (_int_free): Add inexpensive double free test.

1 files changed, 7 insertions, 0 deletions

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 5636d5c..4db4051 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -4201,6 +4201,13 @@ _int_free(mstate av, Void_t* mem)
 
       set_fastchunks(av);
       fb = &(av->fastbins[fastbin_index(size)]);
+      /* Another simple check: make sure the top of the bin is not the
+	 record we are going to add (i.e., double free).  */
+      if (__builtin_expect (*fb == p, 0))
+	{
+	  malloc_printf_nc (check_action, "double free(%p)!\n", mem);
+	  return;
+	}
       p->fd = *fb;
       *fb = p;
     }