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Fix bugs with memory allocation in ego.

cf/cf_loop.c and share/put.c tried to read the next pointer in an
element of a linked list after freeing the element.  ud/ud_copy.c
tried to read beyond the end of the _defs_ array: it only has
_nrexpldefs_ elements, not _nrdefs_ elements.

These bugs caused core dumps on OpenBSD.  Its malloc() put _defs_ near
the end of a page, so reading beyond the end crossed into an unmapped
page.  Its free() wrote junk bytes and changed the next pointer to
0xdfdfdfdfdfdfdfdf.
George Koehler 7 years ago
parent
commit
b1d1b5e1f8
3 changed files with 11 additions and 5 deletions
  1. 5 2
      util/ego/cf/cf_loop.c
  2. 4 1
      util/ego/share/put.c
  3. 2 2
      util/ego/ud/ud_copy.c

+ 5 - 2
util/ego/cf/cf_loop.c

@@ -171,9 +171,12 @@ STATIC collapse_loops(loops_p)
 	for (li1 = Lfirst(*loops_p); li1 != (Lindex) 0; li1 = Lnext(li1,*loops_p)) {
 		lp1 = (loop_p) Lelem(li1);
 		lp1->lp_level = (short) 0;
-		for (li2 = Lfirst(*loops_p); li2 != (Lindex) 0;
-					li2 = Lnext(li2,*loops_p)) {
+		/* Lnext(li2,*loops_p) must happen before
+		 * Lremove(lp2,loops_p) releases the memory for li2.
+		 */
+		for (li2 = Lfirst(*loops_p); li2 != (Lindex) 0;) {
 			lp2 = (loop_p) Lelem(li2);
+			li2 = Lnext(li2,*loops_p);
 			if (lp1 != lp2 && lp1->lp_entry == lp2->lp_entry) {
 			    Ljoin(lp2->LP_BLOCKS,&lp1->LP_BLOCKS);
 			    oldcflpx(lp2->lp_extend);

+ 4 - 1
util/ego/share/put.c

@@ -386,6 +386,7 @@ putunit(kind,p,l,gf,lf)
 	register bblock_p b;
 	register short n = 0;
 	Lindex   pi;
+	bblock_p nextb;
 	loop_p   lp;
 
 	curoutp = gf;
@@ -432,10 +433,12 @@ putunit(kind,p,l,gf,lf)
 	 * after it has been written, because there may be references
 	 * to it from other (later) blocks.
 	 */
-	for (b = p->p_start; b != (bblock_p) 0; b = b->b_next) {
+	for (b = p->p_start; b != (bblock_p) 0; b = nextb) {
 		Ldeleteset(b->b_loops);
 		Ldeleteset(b->b_succ);
 		Ldeleteset(b->b_pred);
+		/* Must read b->b_next before releasing b */
+		nextb = b->b_next;
 		oldbblock(b);
 	}
 	/* Release the memory for the lmap, lbmap, bmap, lpmap tables */

+ 2 - 2
util/ego/ud/ud_copy.c

@@ -59,7 +59,7 @@ STATIC traverse_defs(p,action)
 		def_to_copynr = newtable(nrdefs);
 		cnt = 1;
 	}
-	if (defcnt > nrdefs) return;
+	if (defcnt > nrexpldefs) return;
 	for (b = p->p_start; b != (bblock_p) 0; b = b->b_next) {
 		for (l = b->b_start; l != (line_p) 0; l = l->l_next) {
 			if (defs[defcnt] == l) {
@@ -75,7 +75,7 @@ STATIC traverse_defs(p,action)
 						}
 					}
 				}
-				if (++defcnt > nrdefs) return;
+				if (++defcnt > nrexpldefs) return;
 			}
 		}
 	}