net: dns: dispatcher: Don't use uninitialized entires

In case CONFIG_DNS_RESOLVER_MAX_SERVERS is larger than the actual number of DNS servers configured, some server entries may be left uninitialized. The dispatcher needs to take this into account, otherwise it may cause memory corruptions. Signed-off-by: Robert Lubos <[email protected]>
zephyrproject-rtos · Oct 3, 2024 · 0ed6617 · 0ed6617
1 parent ff5fe19
commit 0ed6617
Showing 1 changed file with 8 additions and 0 deletions.
diff --git a/subsys/net/lib/dns/dispatcher.c b/subsys/net/lib/dns/dispatcher.c
@@ -260,6 +260,10 @@ int dns_dispatcher_register(struct dns_socket_dispatcher *ctx)
 				goto out;
 			}
 
+			if (ctx->fds[i].fd < 0) {
+				continue;
+			}
+
 			if (dispatch_table[ctx->fds[i].fd].ctx == NULL) {
 				dispatch_table[ctx->fds[i].fd].ctx = ctx;
 			}
@@ -297,6 +301,10 @@ int dns_dispatcher_register(struct dns_socket_dispatcher *ctx)
 			goto out;
 		}
 
+		if (ctx->fds[i].fd < 0) {
+			continue;
+		}
+
 		if (dispatch_table[ctx->fds[i].fd].ctx == NULL) {
 			dispatch_table[ctx->fds[i].fd].ctx = ctx;
 		}