malloc: additional unlink hardening for non-small bins [BZ #17344]

Turn two asserts into a conditional call to malloc_printerr.  The
memory locations are accessed later anyway, so the performance
impact is minor.

ChangeLog

@@ -1,3 +1,9 @@
+2014-09-11  Florian Weimer  <fweimer@redhat.com>
+
+	[BZ #17344]
+	* malloc/malloc.c (unlink): Turn asserts into a call to
+	malloc_printerr.
+
 2014-09-11  Tim Lammens  <tim.lammens@gmail.com>
 
 	[BZ #17370]

NEWS

@@ -29,7 +29,7 @@ Version 2.20
   16966, 16967, 16977, 16978, 16984, 16990, 16996, 17009, 17022, 17031,
   17042, 17048, 17050, 17058, 17061, 17062, 17069, 17075, 17078, 17079,
   17084, 17086, 17088, 17092, 17097, 17125, 17135, 17137, 17150, 17153,
-  17187, 17213, 17259, 17261, 17262, 17263, 17319, 17325, 17354.
+  17187, 17213, 17259, 17261, 17262, 17263, 17319, 17325, 17344, 17354.
 
 * Reverted change of ABI data structures for s390 and s390x:
   On s390 and s390x the size of struct ucontext and jmp_buf was increased in

malloc/malloc.c

@@ -1418,8 +1418,10 @@ typedef struct malloc_chunk *mbinptr;
         BK->fd = FD;							      \
         if (!in_smallbin_range (P->size)				      \
             && __builtin_expect (P->fd_nextsize != NULL, 0)) {		      \
-            assert (P->fd_nextsize->bk_nextsize == P);			      \
-            assert (P->bk_nextsize->fd_nextsize == P);			      \
+	    if (__builtin_expect (P->fd_nextsize->bk_nextsize != P, 0)	      \
+		|| __builtin_expect (P->bk_nextsize->fd_nextsize != P, 0))    \
+	      malloc_printerr (check_action,				      \
+			       "corrupted double-linked list (not small)", P);\
             if (FD->fd_nextsize == NULL) {				      \
                 if (P->fd_nextsize == P)				      \
                   FD->fd_nextsize = FD->bk_nextsize = FD;		      \