Make sure strncat is > 0

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@1341 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index fd5971e..e1727de 100755 (executable)
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -3720,9 +3720,13 @@ static int check_user(struct sip_pvt *p, struct sip_request *req, char *cmd, cha
 static int get_msg_text(char *buf, int len, struct sip_request *req)
 {
        int x;
+       int y;
        strcpy(buf, "");
+       y = len - strlen(buf) - 5;
+       if (y < 0)
+               y = 0;
        for (x=0;x<req->lines;x++) {
-               strncat(buf, req->line[x], len - strlen(buf) - 5);
+               strncat(buf, req->line[x], y);
                strcat(buf, "\n");
        }
        return 0;