kernel/tools/testing/selftests/net/af_unix/scm_pidfd.c

// SPDX-License-Identifier: GPL-2.0 OR MIT
#define _GNU_SOURCE
#include <error.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <linux/socket.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/un.h>
#include <sys/signal.h>
#include <sys/types.h>
#include <sys/wait.h>

#include "../../kselftest_harness.h"

#define clean_errno() (errno == 0 ? "None" : strerror(errno))
#define log_err(MSG, ...)                                                   \
	fprintf(stderr, "(%s:%d: errno: %s) " MSG "\n", __FILE__, __LINE__, \
		clean_errno(), ##__VA_ARGS__)

#ifndef SCM_PIDFD
#define SCM_PIDFD 0x04
#endif

static void child_die()
{
	exit(1);
}

static int safe_int(const char *numstr, int *converted)
{
	char *err = NULL;
	long sli;

	errno = 0;
	sli = strtol(numstr, &err, 0);
	if (errno == ERANGE && (sli == LONG_MAX || sli == LONG_MIN))
		return -ERANGE;

	if (errno != 0 && sli == 0)
		return -EINVAL;

	if (err == numstr || *err != '\0')
		return -EINVAL;

	if (sli > INT_MAX || sli < INT_MIN)
		return -ERANGE;

	*converted = (int)sli;
	return 0;
}

static int char_left_gc(const char *buffer, size_t len)
{
	size_t i;

	for (i = 0; i < len; i++) {
		if (buffer[i] == ' ' || buffer[i] == '\t')
			continue;

		return i;
	}

	return 0;
}

static int char_right_gc(const char *buffer, size_t len)
{
	int i;

	for (i = len - 1; i >= 0; i--) {
		if (buffer[i] == ' ' || buffer[i] == '\t' ||
		    buffer[i] == '\n' || buffer[i] == '\0')
			continue;

		return i + 1;
	}

	return 0;
}

static char *trim_whitespace_in_place(char *buffer)
{
	buffer += char_left_gc(buffer, strlen(buffer));
	buffer[char_right_gc(buffer, strlen(buffer))] = '\0';
	return buffer;
}

/* borrowed (with all helpers) from pidfd/pidfd_open_test.c */
static pid_t get_pid_from_fdinfo_file(int pidfd, const char *key, size_t keylen)
{
	int ret;
	char path[512];
	FILE *f;
	size_t n = 0;
	pid_t result = -1;
	char *line = NULL;

	snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", pidfd);

	f = fopen(path, "re");
	if (!f)
		return -1;

	while (getline(&line, &n, f) != -1) {
		char *numstr;

		if (strncmp(line, key, keylen))
			continue;

		numstr = trim_whitespace_in_place(line + 4);
		ret = safe_int(numstr, &result);
		if (ret < 0)
			goto out;

		break;
	}

out:
	free(line);
	fclose(f);
	return result;
}

static int cmsg_check(int fd)
{
	struct msghdr msg = { 0 };
	struct cmsghdr *cmsg;
	struct iovec iov;
	struct ucred *ucred = NULL;
	int data = 0;
	char control[CMSG_SPACE(sizeof(struct ucred)) +
		     CMSG_SPACE(sizeof(int))] = { 0 };
	int *pidfd = NULL;
	pid_t parent_pid;
	int err;

	iov.iov_base = &data;
	iov.iov_len = sizeof(data);

	msg.msg_iov = &iov;
	msg.msg_iovlen = 1;
	msg.msg_control = control;
	msg.msg_controllen = sizeof(control);

	err = recvmsg(fd, &msg, 0);
	if (err < 0) {
		log_err("recvmsg");
		return 1;
	}

	if (msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC)) {
		log_err("recvmsg: truncated");
		return 1;
	}

	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
	     cmsg = CMSG_NXTHDR(&msg, cmsg)) {
		if (cmsg->cmsg_level == SOL_SOCKET &&
		    cmsg->cmsg_type == SCM_PIDFD) {
			if (cmsg->cmsg_len < sizeof(*pidfd)) {
				log_err("CMSG parse: SCM_PIDFD wrong len");
				return 1;
			}

			pidfd = (void *)CMSG_DATA(cmsg);
		}

		if (cmsg->cmsg_level == SOL_SOCKET &&
		    cmsg->cmsg_type == SCM_CREDENTIALS) {
			if (cmsg->cmsg_len < sizeof(*ucred)) {
				log_err("CMSG parse: SCM_CREDENTIALS wrong len");
				return 1;
			}

			ucred = (void *)CMSG_DATA(cmsg);
		}
	}

	/* send(pfd, "x", sizeof(char), 0) */
	if (data != 'x') {
		log_err("recvmsg: data corruption");
		return 1;
	}

	if (!pidfd) {
		log_err("CMSG parse: SCM_PIDFD not found");
		return 1;
	}

	if (!ucred) {
		log_err("CMSG parse: SCM_CREDENTIALS not found");
		return 1;
	}

	/* pidfd from SCM_PIDFD should point to the parent process PID */
	parent_pid =
		get_pid_from_fdinfo_file(*pidfd, "Pid:", sizeof("Pid:") - 1);
	if (parent_pid != getppid()) {
		log_err("wrong SCM_PIDFD %d != %d", parent_pid, getppid());
		return 1;
	}

	return 0;
}

struct sock_addr {
	char sock_name[32];
	struct sockaddr_un listen_addr;
	socklen_t addrlen;
};

FIXTURE(scm_pidfd)
{
	int server;
	pid_t client_pid;
	int startup_pipe[2];
	struct sock_addr server_addr;
	struct sock_addr *client_addr;
};

FIXTURE_VARIANT(scm_pidfd)
{
	int type;
	bool abstract;
};

FIXTURE_VARIANT_ADD(scm_pidfd, stream_pathname)
{
	.type = SOCK_STREAM,
	.abstract = 0,
};

FIXTURE_VARIANT_ADD(scm_pidfd, stream_abstract)
{
	.type = SOCK_STREAM,
	.abstract = 1,
};

FIXTURE_VARIANT_ADD(scm_pidfd, dgram_pathname)
{
	.type = SOCK_DGRAM,
	.abstract = 0,
};

FIXTURE_VARIANT_ADD(scm_pidfd, dgram_abstract)
{
	.type = SOCK_DGRAM,
	.abstract = 1,
};

FIXTURE_SETUP(scm_pidfd)
{
	self->client_addr = mmap(NULL, sizeof(*self->client_addr), PROT_READ | PROT_WRITE,
				 MAP_SHARED | MAP_ANONYMOUS, -1, 0);
	ASSERT_NE(MAP_FAILED, self->client_addr);
}

FIXTURE_TEARDOWN(scm_pidfd)
{
	close(self->server);

	kill(self->client_pid, SIGKILL);
	waitpid(self->client_pid, NULL, 0);

	if (!variant->abstract) {
		unlink(self->server_addr.sock_name);
		unlink(self->client_addr->sock_name);
	}
}

static void fill_sockaddr(struct sock_addr *addr, bool abstract)
{
	char *sun_path_buf = (char *)&addr->listen_addr.sun_path;

	addr->listen_addr.sun_family = AF_UNIX;
	addr->addrlen = offsetof(struct sockaddr_un, sun_path);
	snprintf(addr->sock_name, sizeof(addr->sock_name), "scm_pidfd_%d", getpid());
	addr->addrlen += strlen(addr->sock_name);
	if (abstract) {
		*sun_path_buf = '\0';
		addr->addrlen++;
		sun_path_buf++;
	} else {
		unlink(addr->sock_name);
	}
	memcpy(sun_path_buf, addr->sock_name, strlen(addr->sock_name));
}

static void client(FIXTURE_DATA(scm_pidfd) *self,
		   const FIXTURE_VARIANT(scm_pidfd) *variant)
{
	int cfd;
	socklen_t len;
	struct ucred peer_cred;
	int peer_pidfd;
	pid_t peer_pid;
	int on = 0;

	cfd = socket(AF_UNIX, variant->type, 0);
	if (cfd < 0) {
		log_err("socket");
		child_die();
	}

	if (variant->type == SOCK_DGRAM) {
		fill_sockaddr(self->client_addr, variant->abstract);

		if (bind(cfd, (struct sockaddr *)&self->client_addr->listen_addr, self->client_addr->addrlen)) {
			log_err("bind");
			child_die();
		}
	}

	if (connect(cfd, (struct sockaddr *)&self->server_addr.listen_addr,
		    self->server_addr.addrlen) != 0) {
		log_err("connect");
		child_die();
	}

	on = 1;
	if (setsockopt(cfd, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on))) {
		log_err("Failed to set SO_PASSCRED");
		child_die();
	}

	if (setsockopt(cfd, SOL_SOCKET, SO_PASSPIDFD, &on, sizeof(on))) {
		log_err("Failed to set SO_PASSPIDFD");
		child_die();
	}

	close(self->startup_pipe[1]);

	if (cmsg_check(cfd)) {
		log_err("cmsg_check failed");
		child_die();
	}

	/* skip further for SOCK_DGRAM as it's not applicable */
	if (variant->type == SOCK_DGRAM)
		return;

	len = sizeof(peer_cred);
	if (getsockopt(cfd, SOL_SOCKET, SO_PEERCRED, &peer_cred, &len)) {
		log_err("Failed to get SO_PEERCRED");
		child_die();
	}

	len = sizeof(peer_pidfd);
	if (getsockopt(cfd, SOL_SOCKET, SO_PEERPIDFD, &peer_pidfd, &len)) {
		log_err("Failed to get SO_PEERPIDFD");
		child_die();
	}

	/* pid from SO_PEERCRED should point to the parent process PID */
	if (peer_cred.pid != getppid()) {
		log_err("peer_cred.pid != getppid(): %d != %d", peer_cred.pid, getppid());
		child_die();
	}

	peer_pid = get_pid_from_fdinfo_file(peer_pidfd,
					    "Pid:", sizeof("Pid:") - 1);
	if (peer_pid != peer_cred.pid) {
		log_err("peer_pid != peer_cred.pid: %d != %d", peer_pid, peer_cred.pid);
		child_die();
	}
}

TEST_F(scm_pidfd, test)
{
	int err;
	int pfd;
	int child_status = 0;

	self->server = socket(AF_UNIX, variant->type, 0);
	ASSERT_NE(-1, self->server);

	fill_sockaddr(&self->server_addr, variant->abstract);

	err = bind(self->server, (struct sockaddr *)&self->server_addr.listen_addr, self->server_addr.addrlen);
	ASSERT_EQ(0, err);

	if (variant->type == SOCK_STREAM) {
		err = listen(self->server, 1);
		ASSERT_EQ(0, err);
	}

	err = pipe(self->startup_pipe);
	ASSERT_NE(-1, err);

	self->client_pid = fork();
	ASSERT_NE(-1, self->client_pid);
	if (self->client_pid == 0) {
		close(self->server);
		close(self->startup_pipe[0]);
		client(self, variant);
		exit(0);
	}
	close(self->startup_pipe[1]);

	if (variant->type == SOCK_STREAM) {
		pfd = accept(self->server, NULL, NULL);
		ASSERT_NE(-1, pfd);
	} else {
		pfd = self->server;
	}

	/* wait until the child arrives at checkpoint */
	read(self->startup_pipe[0], &err, sizeof(int));
	close(self->startup_pipe[0]);

	if (variant->type == SOCK_DGRAM) {
		err = sendto(pfd, "x", sizeof(char), 0, (struct sockaddr *)&self->client_addr->listen_addr, self->client_addr->addrlen);
		ASSERT_NE(-1, err);
	} else {
		err = send(pfd, "x", sizeof(char), 0);
		ASSERT_NE(-1, err);
	}

	close(pfd);
	waitpid(self->client_pid, &child_status, 0);
	ASSERT_EQ(0, WIFEXITED(child_status) ? WEXITSTATUS(child_status) : 1);
}

TEST_HARNESS_MAIN