Commit 575a0ae9 authored by Christian Brauner's avatar Christian Brauner

selftests: add tests for pidfd_send_signal()

As suggested by Andrew Morton in [1] add selftests for the new
sys_pidfd_send_signal() syscall:

/* test_pidfd_send_signal_syscall_support */
Test whether the pidfd_send_signal() syscall is supported and the tests can
be run or need to be skipped.

/* test_pidfd_send_signal_simple_success */
Test whether sending a signal via a pidfd works.

/* test_pidfd_send_signal_exited_fail */
Verify that sending a signal to an already exited process fails with ESRCH.

/* test_pidfd_send_signal_recycled_pid_fail */
Verify that a recycled pid cannot be signaled via a pidfd referring to an
already exited process that had the same pid (cf. [2], [3]).

[1]: https://lore.kernel.org/lkml/20181228152012.dbf0508c2508138efc5f2bbe@linux-foundation.org/
[2]: https://lore.kernel.org/lkml/20181230210245.GA30252@mail.hallyn.com/
[3]: https://lore.kernel.org/lkml/20181230232711.7aayb7vnhogbv4co@brauner.io/

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
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: default avatarChristian Brauner <christian@brauner.io>
Reviewed-by: default avatarTycho Andersen <tycho@tycho.ws>
Acked-by: default avatarSerge Hallyn <serge@hallyn.com>
parent 3eb39f47
......@@ -30,6 +30,7 @@ TARGETS += net
TARGETS += netfilter
TARGETS += networking/timestamping
TARGETS += nsfs
TARGETS += pidfd
TARGETS += powerpc
TARGETS += proc
TARGETS += pstore
......
CFLAGS += -g -I../../../../usr/include/
TEST_GEN_PROGS := pidfd_test
include ../lib.mk
/* SPDX-License-Identifier: GPL-2.0 */
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <linux/types.h>
#include <sched.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syscall.h>
#include <sys/mount.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 set_signal_received_on_sigusr1(int sig)
{
if (sig == SIGUSR1)
signal_received = 1;
}
/*
* Straightforward test to see whether pidfd_send_signal() works is to send
* a signal to ourself.
*/
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, set_signal_received_on_sigusr1);
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 int wait_for_pid(pid_t pid)
{
int status, ret;
again:
ret = waitpid(pid, &status, 0);
if (ret == -1) {
if (errno == EINTR)
goto again;
return -1;
}
if (ret != pid)
goto again;
if (!WIFEXITED(status))
return -1;
return WEXITSTATUS(status);
}
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);
(void)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;
}
/*
* The kernel reserves 300 pids via RESERVED_PIDS in kernel/pid.c
* That means, when it wraps around any pid < 300 will be skipped.
* So we need to use a pid > 300 in order to test recycling.
*/
#define PID_RECYCLE 1000
/*
* Maximum number of cycles we allow. This is equivalent to PID_MAX_DEFAULT.
* If users set a higher limit or we have cycled PIDFD_MAX_DEFAULT number of
* times then we skip the test to not go into an infinite loop or block for a
* long time.
*/
#define PIDFD_MAX_DEFAULT 0x8000
/*
* Define a few custom error codes for the child process to clearly indicate
* what is happening. This way we can tell the difference between a system
* error, a test error, etc.
*/
#define PIDFD_PASS 0
#define PIDFD_FAIL 1
#define PIDFD_ERROR 2
#define PIDFD_SKIP 3
#define PIDFD_XFAIL 4
static int test_pidfd_send_signal_recycled_pid_fail(void)
{
int i, ret;
pid_t pid1;
const char *test_name = "pidfd_send_signal signal recycled pid";
ret = unshare(CLONE_NEWPID);
if (ret < 0)
ksft_exit_fail_msg("%s test: Failed to unshare pid namespace\n",
test_name);
ret = unshare(CLONE_NEWNS);
if (ret < 0)
ksft_exit_fail_msg(
"%s test: Failed to unshare mount namespace\n",
test_name);
ret = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0);
if (ret < 0)
ksft_exit_fail_msg("%s test: Failed to remount / private\n",
test_name);
/* pid 1 in new pid namespace */
pid1 = fork();
if (pid1 < 0)
ksft_exit_fail_msg("%s test: Failed to create new process\n",
test_name);
if (pid1 == 0) {
char buf[256];
pid_t pid2;
int pidfd = -1;
(void)umount2("/proc", MNT_DETACH);
ret = mount("proc", "/proc", "proc", 0, NULL);
if (ret < 0)
_exit(PIDFD_ERROR);
/* grab pid PID_RECYCLE */
for (i = 0; i <= PIDFD_MAX_DEFAULT; i++) {
pid2 = fork();
if (pid2 < 0)
_exit(PIDFD_ERROR);
if (pid2 == 0)
_exit(PIDFD_PASS);
if (pid2 == PID_RECYCLE) {
snprintf(buf, sizeof(buf), "/proc/%d", pid2);
ksft_print_msg("pid to recycle is %d\n", pid2);
pidfd = open(buf, O_DIRECTORY | O_CLOEXEC);
}
if (wait_for_pid(pid2))
_exit(PIDFD_ERROR);
if (pid2 >= PID_RECYCLE)
break;
}
/*
* We want to be as predictable as we can so if we haven't been
* able to grab pid PID_RECYCLE skip the test.
*/
if (pid2 != PID_RECYCLE) {
/* skip test */
close(pidfd);
_exit(PIDFD_SKIP);
}
if (pidfd < 0)
_exit(PIDFD_ERROR);
for (i = 0; i <= PIDFD_MAX_DEFAULT; i++) {
char c;
int pipe_fds[2];
pid_t recycled_pid;
int child_ret = PIDFD_PASS;
ret = pipe2(pipe_fds, O_CLOEXEC);
if (ret < 0)
_exit(PIDFD_ERROR);
recycled_pid = fork();
if (recycled_pid < 0)
_exit(PIDFD_ERROR);
if (recycled_pid == 0) {
close(pipe_fds[1]);
(void)read(pipe_fds[0], &c, 1);
close(pipe_fds[0]);
_exit(PIDFD_PASS);
}
/*
* Stop the child so we can inspect whether we have
* recycled pid PID_RECYCLE.
*/
close(pipe_fds[0]);
ret = kill(recycled_pid, SIGSTOP);
close(pipe_fds[1]);
if (ret) {
(void)wait_for_pid(recycled_pid);
_exit(PIDFD_ERROR);
}
/*
* We have recycled the pid. Try to signal it. This
* needs to fail since this is a different process than
* the one the pidfd refers to.
*/
if (recycled_pid == PID_RECYCLE) {
ret = sys_pidfd_send_signal(pidfd, SIGCONT,
NULL, 0);
if (ret && errno == ESRCH)
child_ret = PIDFD_XFAIL;
else
child_ret = PIDFD_FAIL;
}
/* let the process move on */
ret = kill(recycled_pid, SIGCONT);
if (ret)
(void)kill(recycled_pid, SIGKILL);
if (wait_for_pid(recycled_pid))
_exit(PIDFD_ERROR);
switch (child_ret) {
case PIDFD_FAIL:
/* fallthrough */
case PIDFD_XFAIL:
_exit(child_ret);
case PIDFD_PASS:
break;
default:
/* not reached */
_exit(PIDFD_ERROR);
}
/*
* If the user set a custom pid_max limit we could be
* in the millions.
* Skip the test in this case.
*/
if (recycled_pid > PIDFD_MAX_DEFAULT)
_exit(PIDFD_SKIP);
}
/* failed to recycle pid */
_exit(PIDFD_SKIP);
}
ret = wait_for_pid(pid1);
switch (ret) {
case PIDFD_FAIL:
ksft_exit_fail_msg(
"%s test: Managed to signal recycled pid %d\n",
test_name, PID_RECYCLE);
case PIDFD_PASS:
ksft_exit_fail_msg("%s test: Failed to recycle pid %d\n",
test_name, PID_RECYCLE);
case PIDFD_SKIP:
ksft_print_msg("%s test: Skipping test\n", test_name);
ret = 0;
break;
case PIDFD_XFAIL:
ksft_test_result_pass(
"%s test: Failed to signal recycled pid as expected\n",
test_name);
ret = 0;
break;
default /* PIDFD_ERROR */:
ksft_exit_fail_msg("%s test: Error while running tests\n",
test_name);
}
return ret;
}
static int test_pidfd_send_signal_syscall_support(void)
{
int pidfd, ret;
const char *test_name = "pidfd_send_signal check for support";
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);
ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0);
if (ret < 0) {
/*
* pidfd_send_signal() will currently return ENOSYS when
* CONFIG_PROC_FS is not set.
*/
if (errno == ENOSYS)
ksft_exit_skip(
"%s test: pidfd_send_signal() syscall not supported (Ensure that CONFIG_PROC_FS=y is set)\n",
test_name);
ksft_exit_fail_msg("%s test: Failed to send signal\n",
test_name);
}
close(pidfd);
ksft_test_result_pass(
"%s test: pidfd_send_signal() syscall is supported. Tests can be executed\n",
test_name);
return 0;
}
int main(int argc, char **argv)
{
ksft_print_header();
test_pidfd_send_signal_syscall_support();
test_pidfd_send_signal_simple_success();
test_pidfd_send_signal_exited_fail();
test_pidfd_send_signal_recycled_pid_fail();
return ksft_exit_pass();
}
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