dundi: fix NULL dereference.

If a negative (error) return is received from dundi_lookup_internal,
this is not handled correctly when assigning the result to the buffer.
As such, use a signed integer in the assignment and do a proper
comparison.

ASTERISK-21205

Change-Id: I5214ebb6491e2bd14f90c7d3ce229da86888f739

diff --git a/pbx/pbx_dundi.c b/pbx/pbx_dundi.c
index 6cc7711134a99faf06ed2eff6453958a1e42bce8..1ab0676c50fcb1a51c05f6a3271aa7581c6f34e3 100644 (file)
--- a/pbx/pbx_dundi.c
+++ b/pbx/pbx_dundi.c
@@ -4193,7 +4193,7 @@ static unsigned int dundi_result_id;
 
 struct dundi_result_datastore {
        struct dundi_result results[MAX_RESULTS];
-       unsigned int num_results;
+       int num_results;
        unsigned int id;
 };
 
@@ -4325,7 +4325,7 @@ static int dundi_result_read(struct ast_channel *chan, const char *cmd, char *da
        drds = datastore->data;
 
        if (!strcasecmp(args.resultnum, "getnum")) {
-               snprintf(buf, len, "%u", drds->num_results);
+               snprintf(buf, len, "%d", drds->num_results < 0 ? 0 : drds->num_results);
                res = 0;
                goto finish;
        }
@@ -4336,7 +4336,7 @@ static int dundi_result_read(struct ast_channel *chan, const char *cmd, char *da
                goto finish;
        }
 
-       if (num && num <= drds->num_results) {
+       if (num && drds->num_results > 0 && num <= drds->num_results) {
                snprintf(buf, len, "%s/%s", drds->results[num - 1].tech, drds->results[num - 1].dest);
                res = 0;
        } else