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

From: Alexander Mikhalitsyn aleksandr.mikhalitsyn@canonical.com 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@davemloft.net Cc: Eric Dumazet edumazet@google.com Cc: Jakub Kicinski kuba@kernel.org Cc: Paolo Abeni pabeni@redhat.com Cc: Leon Romanovsky leon@kernel.org Cc: David Ahern dsahern@kernel.org Cc: Arnd Bergmann arnd@arndb.de Cc: Kees Cook keescook@chromium.org Cc: Christian Brauner brauner@kernel.org Cc: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org Cc: linux-arch@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Signed-off-by: Alexander Mikhalitsyn aleksandr.mikhalitsyn@canonical.com

---

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