drivers: modem: Fix reference to stack in modem_context_sprint_ip_addr

Changes the modem_context_sprint_ip addr to write into a provided
buffer. This approach fixes a referencing to a non existing stack
variable, without using a lot of stack space.
Tested using the by building all used modems and tested on HW using
IPv4.

Fixes: #38459

Signed-off-by: Sjors Hettinga <s.a.hettinga@gmail.com>

drivers/modem/modem_context.c

@@ -20,23 +20,40 @@ LOG_MODULE_REGISTER(modem_context, CONFIG_MODEM_LOG_LEVEL);
 
 static struct modem_context *contexts[CONFIG_MODEM_CONTEXT_MAX_NUM];
 
-char *modem_context_sprint_ip_addr(const struct sockaddr *addr)
+int modem_context_sprint_ip_addr(const struct sockaddr *addr, char *buf, size_t buf_size)
 {
-	static char buf[NET_IPV6_ADDR_LEN];
+	static const char unknown_str[] = "unk";
 
 	if (addr->sa_family == AF_INET6) {
-		return net_addr_ntop(AF_INET6, &net_sin6(addr)->sin6_addr,
+		if (buf_size < NET_IPV6_ADDR_LEN) {
-				     buf, sizeof(buf));
+			return -ENOMEM;
+		}
+
+		if (net_addr_ntop(AF_INET6, &net_sin6(addr)->sin6_addr,
+					buf, buf_size) == NULL) {
+			return -ENOMEM;
+		}
+		return 0;
 	}
 
 	if (addr->sa_family == AF_INET) {
-		return net_addr_ntop(AF_INET, &net_sin(addr)->sin_addr,
+		if (buf_size < NET_IPV4_ADDR_LEN) {
-				     buf, sizeof(buf));
+			return -ENOMEM;
+		}
+		if (net_addr_ntop(AF_INET, &net_sin(addr)->sin_addr,
+					buf, buf_size) == NULL) {
+			return -ENOMEM;
+		}
+		return 0;
 	}
 
 	LOG_ERR("Unknown IP address family:%d", addr->sa_family);
-	strcpy(buf, "unk");
+
-	return buf;
+	if (buf_size < sizeof(unknown_str)) {
+		return -ENOMEM;
+	}
+	strcpy(buf, unknown_str);
+	return 0;
 }
 
 int modem_context_get_addr_port(const struct sockaddr *addr, uint16_t *port)

drivers/modem/modem_context.h

@@ -91,10 +91,12 @@ struct modem_context {
  * @brief  IP address to string
  *
  * @param  addr: sockaddr to be converted
+ * @param  buf:  Buffer to store IP in string form
+ * @param  buf_size:  buffer size
  *
- * @retval Buffer with IP in string form
+ * @retval 0 if ok, < 0 if error.
  */
-char *modem_context_sprint_ip_addr(const struct sockaddr *addr);
+int modem_context_sprint_ip_addr(const struct sockaddr *addr, char *buf, size_t buf_size);
 
 /**
  * @brief  Get port from IP address

drivers/modem/quectel-bg9x.c

@@ -705,6 +705,7 @@ static int offload_connect(void *obj, const struct sockaddr *addr,
 	struct modem_cmd    cmd[]     = { MODEM_CMD("+QIOPEN: ", on_cmd_atcmdinfo_sockopen, 2U, ",") };
 	char		    buf[sizeof("AT+QIOPEN=#,##,###,####.####.####.####,######")] = {0};
 	int		    ret;
+	char		    ip_str[NET_IPV6_ADDR_LEN];
 
 	if (sock->id < mdata.socket_config.base_socket_num - 1) {
 		LOG_ERR("Invalid socket_id(%d) from fd:%d",
@@ -735,9 +736,18 @@ static int offload_connect(void *obj, const struct sockaddr *addr,
 
 	k_sem_reset(&mdata.sem_sock_conn);
 
+	ret = modem_context_sprint_ip_addr(addr, ip_str, sizeof(ip_str));
+	if (ret != 0) {
+		LOG_ERR("Error formatting IP string %d", ret);
+		LOG_ERR("Closing the socket!!!");
+		socket_close(sock);
+		errno = -ret;
+		return -1;
+	}
+
 	/* Formulate the complete string. */
 	snprintk(buf, sizeof(buf), "AT+QIOPEN=%d,%d,\"%s\",\"%s\",%d,0,0", 1, sock->sock_fd, protocol,
-		 modem_context_sprint_ip_addr(addr), dst_port);
+		ip_str, dst_port);
 
 	/* Send out the command. */
 	ret = modem_cmd_send(&mctx.iface, &mctx.cmd_handler,

drivers/modem/ublox-sara-r4.c

@@ -358,10 +358,18 @@ static ssize_t send_socket_data(void *obj,
 	mdata.sock_written = 0;
 
 	if (sock->ip_proto == IPPROTO_UDP) {
+		char ip_str[NET_IPV6_ADDR_LEN];
+
+		ret = modem_context_sprint_ip_addr(dst_addr, ip_str, sizeof(ip_str));
+		if (ret != 0) {
+			LOG_ERR("Error formatting IP string %d", ret);
+			goto exit;
+		}
+
 		ret = modem_context_get_addr_port(dst_addr, &dst_port);
 		snprintk(send_buf, sizeof(send_buf),
 			 "AT+USOST=%d,\"%s\",%u,%zu", sock->id,
-			 modem_context_sprint_ip_addr(dst_addr),
+			 ip_str,
 			 dst_port, buf_len);
 	} else {
 		snprintk(send_buf, sizeof(send_buf), "AT+USOWR=%d,%zu",
@@ -1538,6 +1546,7 @@ static int offload_connect(void *obj, const struct sockaddr *addr,
 	int ret;
 	char buf[sizeof("AT+USOCO=#,!###.###.###.###!,#####,#\r")];
 	uint16_t dst_port = 0U;
+	char ip_str[NET_IPV6_ADDR_LEN];
 
 	if (!addr) {
 		errno = EINVAL;
@@ -1574,8 +1583,15 @@ static int offload_connect(void *obj, const struct sockaddr *addr,
 		return 0;
 	}
 
+	ret = modem_context_sprint_ip_addr(addr, ip_str, sizeof(ip_str));
+	if (ret != 0) {
+		errno = -ret;
+		LOG_ERR("Error formatting IP string %d", ret);
+		return -1;
+	}
+
 	snprintk(buf, sizeof(buf), "AT+USOCO=%d,\"%s\",%d", sock->id,
-		 modem_context_sprint_ip_addr(addr), dst_port);
+		ip_str, dst_port);
 	ret = modem_cmd_send(&mctx.iface, &mctx.cmd_handler,
 			     NULL, 0U, buf,
 			     &mdata.sem_response, MDM_CMD_CONN_TIMEOUT);