From 3e69928f1332a631345709c72d9161f2d2ea8fbb Mon Sep 17 00:00:00 2001
From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Fri, 7 May 2021 21:27:33 +0200
Subject: [PATCH] common: ipc_single_command can return NULL

Especially printf's %s with NULL value is undefined behavior.
---
 common/ipc-client.c | 12 +++++++++---
 sway/main.c         |  2 +-
 swaybar/ipc.c       |  5 ++++-
 swaymsg/main.c      |  8 ++++++++
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/common/ipc-client.c b/common/ipc-client.c
index 78dec010..088347eb 100644
--- a/common/ipc-client.c
+++ b/common/ipc-client.c
@@ -153,9 +153,15 @@ char *ipc_single_command(int socketfd, uint32_t type, const char *payload, size_
 	}
 
 	struct ipc_response *resp = ipc_recv_response(socketfd);
-	char *response = resp->payload;
-	*len = resp->size;
-	free(resp);
+	char *response;
+	if (resp == NULL) {
+		response = NULL;
+		*len = 0;
+	} else {
+		response = resp->payload;
+		*len = resp->size;
+		free(resp);
+	}
 
 	return response;
 }
diff --git a/sway/main.c b/sway/main.c
index e367ed36..95b522c5 100644
--- a/sway/main.c
+++ b/sway/main.c
@@ -89,7 +89,7 @@ void run_as_ipc_client(char *command, char *socket_path) {
 	int socketfd = ipc_open_socket(socket_path);
 	size_t len = strlen(command);
 	char *resp = ipc_single_command(socketfd, IPC_COMMAND, command, &len);
-	printf("%s\n", resp);
+	printf("%s\n", resp == NULL ? "(null)" : resp);
 	free(resp);
 	close(socketfd);
 }
diff --git a/swaybar/ipc.c b/swaybar/ipc.c
index 3800a1dd..d5cf6a31 100644
--- a/swaybar/ipc.c
+++ b/swaybar/ipc.c
@@ -344,6 +344,9 @@ bool ipc_get_workspaces(struct swaybar *bar) {
 	size_t len = 0;
 	char *res = ipc_single_command(bar->ipc_socketfd,
 			IPC_GET_WORKSPACES, NULL, &len);
+	if (res == NULL) {
+		return false;
+	}
 	json_object *results = json_tokener_parse(res);
 	if (!results) {
 		free(res);
@@ -418,7 +421,7 @@ bool ipc_initialize(struct swaybar *bar) {
 	size_t len = strlen(bar->id);
 	char *res = ipc_single_command(bar->ipc_socketfd,
 			IPC_GET_BAR_CONFIG, bar->id, &len);
-	if (!ipc_parse_config(bar->config, res)) {
+	if (res == NULL || !ipc_parse_config(bar->config, res)) {
 		free(res);
 		return false;
 	}
diff --git a/swaymsg/main.c b/swaymsg/main.c
index 993e08f0..95f5695f 100644
--- a/swaymsg/main.c
+++ b/swaymsg/main.c
@@ -478,6 +478,14 @@ int main(int argc, char **argv) {
 	ipc_set_recv_timeout(socketfd, timeout);
 	size_t len = strlen(command);
 	char *resp = ipc_single_command(socketfd, type, command, &len);
+	if (resp == NULL) {
+		if (!quiet) {
+			sway_log(SWAY_ERROR, "Failed to receive reply");
+		}
+		close(socketfd);
+		free(socket_path);
+		return 1;
+	}
 
 	// pretty print the json
 	json_object *obj = json_tokener_parse(resp);