test: verify fdinfo for pidfd of reaped process

Test that the fdinfo field of a pidfd referring to a dead process
correctly shows Pid: -1 and NSpid: -1.

Cc: Christian Kellner <christian@kellner.me>
Cc: linux-kselftest@vger.kernel.org
Reviewed-by: Christian Kellner <christian@kellner.me>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20191017101832.5985-2-christian.brauner@ubuntu.com

diff --git a/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c b/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c
index 3721be994abdc2e7bf7d2d7a09d9726d4df387c4..22558524f71c34da86e9e0dacc5a73c523254e72 100644 (file)
--- a/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c
@@ -113,11 +113,15 @@ static struct child clone_newns(int (*fn)(void *), void *args,
        return ret;
 }
 
+static inline void child_close(struct child *child)
+{
+       close(child->fd);
+}
+
 static inline int child_join(struct child *child, struct error *err)
 {
        int r;
 
-       (void)close(child->fd);
        r = wait_for_pid(child->pid);
        if (r < 0)
                error_set(err, PIDFD_ERROR, "waitpid failed (ret %d, errno %d)",
@@ -128,6 +132,12 @@ static inline int child_join(struct child *child, struct error *err)
        return r;
 }
 
+static inline int child_join_close(struct child *child, struct error *err)
+{
+       child_close(child);
+       return child_join(child, err);
+}
+
 static inline void trim_newline(char *str)
 {
        char *pos = strrchr(str, '\n');
@@ -136,8 +146,8 @@ static inline void trim_newline(char *str)
                *pos = '\0';
 }
 
-static int verify_fdinfo_nspid(int pidfd, struct error *err,
-                              const char *expect, ...)
+static int verify_fdinfo(int pidfd, struct error *err, const char *prefix,
+                        size_t prefix_len, const char *expect, ...)
 {
        char buffer[512] = {0, };
        char path[512] = {0, };
@@ -160,17 +170,20 @@ static int verify_fdinfo_nspid(int pidfd, struct error *err,
                                 pidfd);
 
        while (getline(&line, &n, f) != -1) {
-               if (strncmp(line, "NSpid:", 6))
+               char *val;
+
+               if (strncmp(line, prefix, prefix_len))
                        continue;
 
                found = 1;
 
-               r = strcmp(line + 6, buffer);
+               val = line + prefix_len;
+               r = strcmp(val, buffer);
                if (r != 0) {
                        trim_newline(line);
                        trim_newline(buffer);
-                       error_set(err, PIDFD_FAIL, "NSpid: '%s' != '%s'",
-                                 line + 6, buffer);
+                       error_set(err, PIDFD_FAIL, "%s '%s' != '%s'",
+                                 prefix, val, buffer);
                }
                break;
        }
@@ -179,8 +192,8 @@ static int verify_fdinfo_nspid(int pidfd, struct error *err,
        fclose(f);
 
        if (found == 0)
-               return error_set(err, PIDFD_FAIL, "NSpid not found for fd %d",
-                                pidfd);
+               return error_set(err, PIDFD_FAIL, "%s not found for fd %d",
+                                prefix, pidfd);
 
        return PIDFD_PASS;
 }
@@ -213,7 +226,7 @@ static int child_fdinfo_nspid_test(void *args)
        }
 
        pidfd = *(int *)args;
-       r = verify_fdinfo_nspid(pidfd, &err, "\t0\n");
+       r = verify_fdinfo(pidfd, &err, "NSpid:", 6, "\t0\n");
 
        if (r != PIDFD_PASS)
                ksft_print_msg("NSpid fdinfo check failed: %s\n", err.msg);
@@ -242,24 +255,42 @@ static void test_pidfd_fdinfo_nspid(void)
        /* The children will have pid 1 in the new pid namespace,
         * so the line must be 'NSPid:\t<pid>\t1'.
         */
-       verify_fdinfo_nspid(a.fd, &err, "\t%d\t%d\n", a.pid, 1);
-       verify_fdinfo_nspid(b.fd, &err, "\t%d\t%d\n", b.pid, 1);
+       verify_fdinfo(a.fd, &err, "NSpid:", 6, "\t%d\t%d\n", a.pid, 1);
+       verify_fdinfo(b.fd, &err, "NSpid:", 6, "\t%d\t%d\n", b.pid, 1);
 
        /* wait for the process, check the exit status and set
         * 'err' accordingly, if it is not already set.
         */
+       child_join_close(&a, &err);
+       child_join_close(&b, &err);
+
+       error_report(&err, test_name);
+}
+
+static void test_pidfd_dead_fdinfo(void)
+{
+       struct child a;
+       struct error err = {0, };
+       const char *test_name = "pidfd check fdinfo for dead process";
+
+       /* Create a new child in a new pid and mount namespace */
+       a = clone_newns(child_fdinfo_nspid_test, NULL, &err);
+       error_check(&err, test_name);
        child_join(&a, &err);
-       child_join(&b, &err);
 
+       verify_fdinfo(a.fd, &err, "Pid:", 4, "\t-1\n");
+       verify_fdinfo(a.fd, &err, "NSpid:", 6, "\t-1\n");
+       child_close(&a);
        error_report(&err, test_name);
 }
 
 int main(int argc, char **argv)
 {
        ksft_print_header();
-       ksft_set_plan(1);
+       ksft_set_plan(2);
 
        test_pidfd_fdinfo_nspid();
+       test_pidfd_dead_fdinfo();
 
        return ksft_exit_pass();
 }