diff -r b6ed2505d6cf -r b9714d958e89 mercurial/mpatch.c
--- a/mercurial/mpatch.c	Wed Mar 16 17:29:29 2016 -0700
+++ b/mercurial/mpatch.c	Wed Mar 16 17:30:26 2016 -0700
@@ -215,10 +215,10 @@
 		lt->start = getbe32(bin + pos);
 		lt->end = getbe32(bin + pos + 4);
 		lt->len = getbe32(bin + pos + 8);
-		if (lt->start > lt->end)
-			break; /* sanity check */
 		lt->data = bin + pos + 12;
 		pos += 12 + lt->len;
+		if (lt->start > lt->end || lt->len < 0)
+			break; /* sanity check */
 		lt++;
 	}