[PATCH v2 2/2] selftests/exec: add a test to enforce execveat()'s comm

[Tycho Andersen]

From: Tycho Andersen <tander...@netflix.com>

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

Signed-off-by: Tycho Andersen <tander...@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