[PATCH 8/9] batctl: tcpdump: reject invalid packet type arguments

The strtol error handling is rather complicated and it is not only about
checking the return value. The possible error indicators are:

* endptr is NULL
* endptr is not pointing to end delimiter
* endptr is pointing at nptr (because it might have been an empty string)
* returned value is larger/smaller than the expected maximum/minimum value
  range

The first tree conditions were not checked even when it is a potential
problem for multiple places. And the user was never informed about the
parsing errors. The old value was simply used.

Perform the needed validation steps and stop with an user readable error on
parsing problems. At the same time, switch to the unsigned number parsing
function strtoul because no negative numbers are allowed as inputs.

Fixes: fca4ef98aa99 ("change mac convert functions, add icmp packet output")
Fixes: c6ed60c0f6fd ("batctl: tcpdump - add option to select all packet types except specified")
Signed-off-by: Sven Eckelmann <[email protected]>
---
 tcpdump.c | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/tcpdump.c b/tcpdump.c
index f9fb0c1..48744ea 100644
--- a/tcpdump.c
+++ b/tcpdump.c
@@ -1506,12 +1506,13 @@ static int tcpdump(struct state *state __maybe_unused, int argc, char **argv)
 	fd_set tmp_wait_sockets;
 	int ret = EXIT_FAILURE;
 	fd_set wait_sockets;
+	unsigned long tmp;
 	struct timeval tv;
 	int max_sock = 0;
 	ssize_t read_len;
+	char *endptr;
 	int optchar;
 	int res;
-	int tmp;
 
 	dump_level = dump_level_all;
 
@@ -1527,14 +1528,28 @@ static int tcpdump(struct state *state __maybe_unused, int argc, char **argv)
 			read_opt &= ~USE_BAT_HOSTS;
 			break;
 		case 'p':
-			tmp = strtol(optarg, NULL, 10);
-			if (tmp > 0 && tmp <= dump_level_all)
-				dump_level = tmp;
+			tmp = strtoul(optarg, &endptr, 10);
+			if (!endptr || *endptr != '\0' || endptr == optarg ||
+			    tmp == 0 || tmp > dump_level_all) {
+				fprintf(stderr,
+					"Error - the supplied packet type is invalid: %s\n",
+					optarg);
+				tcpdump_usage();
+				return EXIT_FAILURE;
+			}
+			dump_level = tmp;
 			break;
 		case 'x':
-			tmp = strtol(optarg, NULL, 10);
-			if (tmp > 0 && tmp <= dump_level_all)
-				dump_level &= ~tmp;
+			tmp = strtoul(optarg, &endptr, 10);
+			if (!endptr || *endptr != '\0' || endptr == optarg ||
+			    tmp == 0 || tmp > dump_level_all) {
+				fprintf(stderr,
+					"Error - the supplied packet type is invalid: %s\n",
+					optarg);
+				tcpdump_usage();
+				return EXIT_FAILURE;
+			}
+			dump_level &= ~tmp;
 			break;
 		default:
 			tcpdump_usage();

-- 
2.47.3