[tor-commits] [tor/master] Prop140: Fix a crash bug.

[nickm at torproject.org]

commit 12d428aaff6d90cadeaca12367f4e14fa673e51c
Author: Nick Mathewson <nickm at torproject.org>
Date:   Tue Mar 7 16:06:03 2017 -0500

    Prop140: Fix a crash bug.
    
    Found while fuzzing: this could occur if we tried to copy a
    nonexistent "line 0" while applying a diff.
---
 src/or/consdiff.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/or/consdiff.c b/src/or/consdiff.c
index 16933de..c33bad1 100644
--- a/src/or/consdiff.c
+++ b/src/or/consdiff.c
@@ -742,7 +742,7 @@ apply_ed_diff(const smartlist_t *cons1, const smartlist_t *diff,
     }
 
     /* Add unchanged lines. */
-    for (; j > end; --j) {
+    for (; j && j > end; --j) {
       const char *cons_line = smartlist_get(cons1, j-1);
       smartlist_add(cons2, tor_strdup(cons_line));
     }