From 345c35a6361f9fb30cb4a2f613ec3ff392a0d8be Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sun, 16 Apr 2017 16:59:01 +0100
Subject: ipif: eat_optionalstr: do not crash on end of argument list

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 ipif/service.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/ipif/service.c b/ipif/service.c
index b401a5c..7821a46 100644
--- a/ipif/service.c
+++ b/ipif/service.c
@@ -329,13 +329,17 @@ static char *eat_optionalstr(const char **argp,
 			     const char *def) {
   ptrdiff_t len;
   const char *start= *argp;
-  const char *comma= strchr(start, ',');
-  if (comma) {
-    len= comma - start;
-    *argp= comma + 1;
+  if (!start) {
+    len = 0;
   } else {
-    len= strlen(start);
-    *argp= start + len;
+    const char *comma= strchr(start, ',');
+    if (comma) {
+      len= comma - start;
+      *argp= comma + 1;
+    } else {
+      len= strlen(start);
+      *argp= start + len;
+    }
   }
   if (!len) {
     start= def;
-- 
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