ipif: eat_optionalstr: do not crash on end of argument list

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

1 files 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;