Re: [PATCH net-next v2 3/3] selftests: net: add SCM_PIDFD / SO_PEERPIDFD test

From: Kuniyuki Iwashima
Date: Tue Mar 21 2023 - 20:48:20 EST

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From: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
Date: Tue, 21 Mar 2023 19:33:42 +0100
> Basic test to check consistency between:
> - SCM_CREDENTIALS and SCM_PIDFD
> - SO_PEERCRED and SO_PEERPIDFD
>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: Leon Romanovsky <leon@xxxxxxxxxx>
> Cc: David Ahern <dsahern@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: linux-arch@xxxxxxxxxxxxxxx
> Cc: linux-kselftest@xxxxxxxxxxxxxxx
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
> ---
> tools/testing/selftests/net/.gitignore | 1 +
> tools/testing/selftests/net/af_unix/Makefile | 3 +-
> .../testing/selftests/net/af_unix/scm_pidfd.c | 336 ++++++++++++++++++
> 3 files changed, 339 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/net/af_unix/scm_pidfd.c
>
> diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore
> index a6911cae368c..f2d23a1df596 100644
> --- a/tools/testing/selftests/net/.gitignore
> +++ b/tools/testing/selftests/net/.gitignore
> @@ -25,6 +25,7 @@ reuseport_bpf_cpu
> reuseport_bpf_numa
> reuseport_dualstack
> rxtimestamp
> +scm_pidfd
> sk_bind_sendto_listen
> sk_connect_zero_addr
> socket
> diff --git a/tools/testing/selftests/net/af_unix/Makefile b/tools/testing/selftests/net/af_unix/Makefile
> index 1e4b397cece6..221c387a7d7f 100644
> --- a/tools/testing/selftests/net/af_unix/Makefile
> +++ b/tools/testing/selftests/net/af_unix/Makefile
> @@ -1,3 +1,4 @@
> -TEST_GEN_PROGS := diag_uid test_unix_oob unix_connect
> +CFLAGS += $(KHDR_INCLUDES)
> +TEST_GEN_PROGS := diag_uid test_unix_oob unix_connect scm_pidfd
>
> include ../../lib.mk
> diff --git a/tools/testing/selftests/net/af_unix/scm_pidfd.c b/tools/testing/selftests/net/af_unix/scm_pidfd.c
> new file mode 100644
> index 000000000000..fa502510ee9e
> --- /dev/null
> +++ b/tools/testing/selftests/net/af_unix/scm_pidfd.c
> @@ -0,0 +1,336 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define _GNU_SOURCE
> +#include <error.h>
> +#include <limits.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"

Could you rewrite with kselftest ?
https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html

Also, it would be better to have all combinations as FIXTURE_VARIANT()
covered by unix_passcred_enabled() like

(self, peer) = (0, 0), (SO_PASSPIDFD, 0), (0, SO_PASSPIDFD),
(SO_PASSPIDFD, SO_PASSPIDFD), ...
(SO_PASSPIDFD, SO_PEERCRED), ...

Thanks,
Kuniyuki

> +
> +#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 pid_t client_pid;
> +static char sock_name[32];
> +
> +static void die(int status)
> +{
> + unlink(sock_name);
> + kill(client_pid, SIGTERM);
> + exit(status);
> +}
> +
> +static void child_die()
> +{
> + kill(getppid(), SIGTERM);
> + 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;
> +}
> +
> +void client(struct sockaddr_un *listen_addr)
> +{
> + int cfd;
> + socklen_t len;
> + struct ucred peer_cred;
> + int peer_pidfd;
> + pid_t peer_pid;
> + int on = 0;
> +
> + cfd = socket(AF_UNIX, SOCK_STREAM, 0);
> + if (cfd < 0) {
> + log_err("socket");
> + child_die();
> + }
> +
> + if (connect(cfd, (struct sockaddr *)listen_addr,
> + sizeof(*listen_addr)) != 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();
> + }
> +
> + if (cmsg_check(cfd)) {
> + log_err("cmsg_check failed");
> + child_die();
> + }
> +
> + 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("Failed to get SO_PEERPIDFD");
> + child_die();
> + }
> +
> + peer_pid = get_pid_from_fdinfo_file(peer_pidfd,
> + "Pid:", sizeof("Pid:") - 1);
> + if (peer_pid != peer_cred.pid) {
> + log_err("Failed to get SO_PEERPIDFD");
> + child_die();
> + }
> +}
> +
> +int main(int argc, char **argv)
> +{
> + int lfd, pfd;
> + int child_status = 0;
> + struct sockaddr_un listen_addr;
> +
> + lfd = socket(AF_UNIX, SOCK_STREAM, 0);
> + if (lfd < 0) {
> + perror("socket");
> + exit(1);
> + }
> +
> + memset(&listen_addr, 0, sizeof(listen_addr));
> + listen_addr.sun_family = AF_UNIX;
> + sprintf(sock_name, "scm_pidfd_%d", getpid());
> + unlink(sock_name);
> + strcpy(listen_addr.sun_path, sock_name);
> +
> + if ((bind(lfd, (struct sockaddr *)&listen_addr, sizeof(listen_addr))) !=
> + 0) {
> + perror("socket bind failed");
> + exit(1);
> + }
> +
> + if (listen(lfd, 1) < 0) {
> + perror("listen");
> + exit(1);
> + }
> +
> + client_pid = fork();
> + if (client_pid < 0) {
> + perror("fork");
> + exit(1);
> + }
> +
> + if (client_pid == 0) {
> + client(&listen_addr);
> + exit(0);
> + }
> +
> + pfd = accept(lfd, NULL, NULL);
> + if (pfd < 0) {
> + perror("accept");
> + die(1);
> + }
> +
> + if (send(pfd, "x", sizeof(char), 0) < 0) {
> + perror("send");
> + die(1);
> + }
> +
> + waitpid(client_pid, &child_status, 0);
> + die(WIFEXITED(child_status) ? WEXITSTATUS(child_status) : 1);
> + die(0);
> +}
> \ No newline at end of file
> --
> 2.34.1

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