[PATCH v3 2/2] selftests/exec: add a test to enforce execveat()'s comm

[Tycho Andersen <tycho@tycho.pizza>]

From: Tycho Andersen <tandersen@netflix.com>

We want to ensure that /proc/self/comm stays useful for execveat() callers.

Signed-off-by: Tycho Andersen <tandersen@netflix.com>
---
 tools/testing/selftests/exec/execveat.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/tools/testing/selftests/exec/execveat.c b/tools/testing/selftests/exec/execveat.c
index 071e03532cba..091029f4ca9b 100644
--- a/tools/testing/selftests/exec/execveat.c
+++ b/tools/testing/selftests/exec/execveat.c
@@ -419,6 +419,9 @@ int main(int argc, char **argv)
 	if (argc >= 2) {
 		/* If we are invoked with an argument, don't run tests. */
 		const char *in_test = getenv("IN_TEST");
+		/* TASK_COMM_LEN == 16 */
+		char buf[32];
+		int fd;
 
 		if (verbose) {
 			ksft_print_msg("invoked with:\n");
@@ -432,6 +435,28 @@ int main(int argc, char **argv)
 			return 1;
 		}
 
+		fd = open("/proc/self/comm", O_RDONLY);
+		if (fd < 0) {
+			perror("open comm");
+			return 1;
+		}
+
+		if (read(fd, buf, sizeof(buf)) < 0) {
+			close(fd);
+			perror("read comm");
+			return 1;
+		}
+		close(fd);
+
+		/*
+		 * /proc/self/comm should fail to convert to an integer, i.e.
+		 * atoi() should return 0.
+		 */
+		if (atoi(buf) != 0) {
+			ksft_print_msg("bad /proc/self/comm: %s", buf);
+			return 1;
+		}
+
 		/* Use the final argument as an exit code. */
 		rc = atoi(argv[argc - 1]);
 		exit(rc);
-- 
2.34.1