Re: [PATCH v6 2/2] selftests: add tests for pidfd_send_signal()

["Serge E. Hallyn" <serge@hallyn.com>]

On Sat, Dec 29, 2018 at 11:27:56PM +0100, Christian Brauner wrote:
> 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>

Acked-by: Serge Hallyn <serge@hallyn.com>

Not saying you need to do this, but it would be neat if you could test
sending to a pid which has been recycled :)

> 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