scan: error on missing conversion char

Don't read invalid memory

Reported-by: Ryan Whitworth <me@ryanwhitworth.com>
Signed-off-by: Steve Bennett <steveb@workware.net.au>

1 files changed, 6 insertions, 1 deletions

diff --git a/jim.c b/jim.c
index d324e56..b857865 100644
--- a/jim.c
+++ b/jim.c
@@ -9890,9 +9890,14 @@ static int SetScanFmtFromAny(Jim_Interp *interp, Jim_Obj *objPtr)
         }
         else {
             /* Remember any valid modifier if given */
-            if (strchr("hlL", *fmt) != 0)
+            if (fmt < fmtEnd && strchr("hlL", *fmt))
                 descr->modifier = tolower((int)*fmt++);
 
+            if (fmt >= fmtEnd) {
+                fmtObj->error = "missing scan conversion character";
+                return JIM_ERR;
+            }
+
             descr->type = *fmt;
             if (strchr("efgcsndoxui", *fmt) == 0) {
                 fmtObj->error = "bad scan conversion character";