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Subject[PATCH v6 2/2] selftests: add tests for pidfd_send_signal()
Date
As suggested by Andrew Morton in [1] add selftests for the new
sys_pidfd_send_signal() syscall.
This tests whether we can send a signal to an existing process and whether
sending a signal to a process that has already exited fails with ESRCH.

[1]: https://lore.kernel.org/lkml/20181228152012.dbf0508c2508138efc5f2bbe@linux-foundation.org/

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Jann Horn <jannh@google.com>
Cc: Andy Lutomirsky <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Christian Brauner <christian@brauner.io>
---
/* Changelog */
v6:
- patch introduced
v5..v0:
- patch not present
---
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/pidfd/Makefile | 6 +
tools/testing/selftests/pidfd/pidfd_test.c | 130 +++++++++++++++++++++
3 files changed, 137 insertions(+)
create mode 100644 tools/testing/selftests/pidfd/Makefile
create mode 100644 tools/testing/selftests/pidfd/pidfd_test.c

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 24b9934fb269..63b0d8a0ebf7 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -27,6 +27,7 @@ TARGETS += net
TARGETS += netfilter
TARGETS += networking/timestamping
TARGETS += nsfs
+TARGETS += pidfd
TARGETS += powerpc
TARGETS += proc
TARGETS += pstore
diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile
new file mode 100644
index 000000000000..deaf8073bc06
--- /dev/null
+++ b/tools/testing/selftests/pidfd/Makefile
@@ -0,0 +1,6 @@
+CFLAGS += -g -I../../../../usr/include/
+
+TEST_GEN_PROGS := pidfd_test
+
+include ../lib.mk
+
diff --git a/tools/testing/selftests/pidfd/pidfd_test.c b/tools/testing/selftests/pidfd/pidfd_test.c
new file mode 100644
index 000000000000..edcd59979b10
--- /dev/null
+++ b/tools/testing/selftests/pidfd/pidfd_test.c
@@ -0,0 +1,130 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/types.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "../kselftest.h"
+
+static inline int sys_pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
+ unsigned int flags)
+{
+ return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags);
+}
+
+static int signal_received;
+
+static void do_exit_success(int sig)
+{
+ signal_received = 1;
+}
+
+/*
+ * Straightforward test to see whether pidfd_send_signal() works is to send
+ * a signal to ourselves.
+ */
+static int test_pidfd_send_signal_simple_success(void)
+{
+ int pidfd, ret;
+ const char *test_name = "pidfd_send_signal send SIGUSR1";
+
+ pidfd = open("/proc/self", O_DIRECTORY | O_CLOEXEC);
+ if (pidfd < 0)
+ ksft_exit_fail_msg(
+ "%s test: Failed to open process file descriptor\n",
+ test_name);
+
+ signal(SIGUSR1, do_exit_success);
+
+ ret = sys_pidfd_send_signal(pidfd, SIGUSR1, NULL, 0);
+ close(pidfd);
+ if (ret < 0)
+ ksft_exit_fail_msg("%s test: Failed to send signal\n",
+ test_name);
+
+ if (signal_received != 1)
+ ksft_exit_fail_msg("%s test: Failed to receive signal\n",
+ test_name);
+
+ signal_received = 0;
+ ksft_test_result_pass("%s test: Sent signal\n", test_name);
+ return 0;
+}
+
+static void wait_for_pid(pid_t pid)
+{
+ int status, ret;
+
+again:
+ ret = waitpid(pid, &status, 0);
+ if (ret == -1) {
+ if (errno == EINTR)
+ goto again;
+
+ return;
+ }
+
+ if (ret != pid)
+ goto again;
+}
+
+static int test_pidfd_send_signal_exited_fail(void)
+{
+ int pidfd, ret, saved_errno;
+ char buf[256];
+ pid_t pid;
+ const char *test_name = "pidfd_send_signal signal exited process";
+
+ pid = fork();
+ if (pid < 0)
+ ksft_exit_fail_msg("%s test: Failed to create new process\n",
+ test_name);
+
+ if (pid == 0)
+ _exit(EXIT_SUCCESS);
+
+ snprintf(buf, sizeof(buf), "/proc/%d", pid);
+
+ pidfd = open(buf, O_DIRECTORY | O_CLOEXEC);
+
+ wait_for_pid(pid);
+
+ if (pidfd < 0)
+ ksft_exit_fail_msg(
+ "%s test: Failed to open process file descriptor\n",
+ test_name);
+
+ ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0);
+ saved_errno = errno;
+ close(pidfd);
+ if (ret == 0)
+ ksft_exit_fail_msg(
+ "%s test: Managed to send signal to process even though it should have failed\n",
+ test_name);
+
+ if (saved_errno != ESRCH)
+ ksft_exit_fail_msg(
+ "%s test: Expected to receive ESRCH as errno value but received %d instead\n",
+ test_name, saved_errno);
+
+ ksft_test_result_pass("%s test: Failed to send signal as expected\n",
+ test_name);
+ return 0;
+}
+
+int main(int argc, char **argv)
+{
+ ksft_print_header();
+
+ test_pidfd_send_signal_simple_success();
+ test_pidfd_send_signal_exited_fail();
+
+ return ksft_exit_pass();
+}
--
2.19.1
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