[PATCH v2 5/5] tests: add pidfd_open() tests

From: Christian Brauner
Date: Fri Mar 29 2019 - 11:54:57 EST

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This adds testing for pidfd_open():
- test that no invalid flags can be passed to pidfd_open()
- test that no invalid pid can be passed to pidfd_open()
- test that a pidfd can be retrieved with pidfd_open()
- test whether a pidfd can be converted into an fd to /proc/<pid> to get
metadata access
- test that a pidfd retrieved based on a pid that has been recycled cannot
be converted into /proc/<pid> for that recycled pid

Signed-off-by: Christian Brauner <christian@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@xxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Cc: Jonathan Kowalski <bl0pbl33p@xxxxxxxxx>
Cc: "Dmitry V. Levin" <ldv@xxxxxxxxxxxx>
Cc: Andy Lutomirsky <luto@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Nagarathnam Muthusamy <nagarathnam.muthusamy@xxxxxxxxxx>
Cc: Aleksa Sarai <cyphar@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/pidfd/Makefile | 2 +-
tools/testing/selftests/pidfd/pidfd.h | 57 +++
.../testing/selftests/pidfd/pidfd_open_test.c | 361 ++++++++++++++++++
tools/testing/selftests/pidfd/pidfd_test.c | 41 +-
4 files changed, 420 insertions(+), 41 deletions(-)
create mode 100644 tools/testing/selftests/pidfd/pidfd.h
create mode 100644 tools/testing/selftests/pidfd/pidfd_open_test.c

diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile
index deaf8073bc06..b36c0be70848 100644
--- a/tools/testing/selftests/pidfd/Makefile
+++ b/tools/testing/selftests/pidfd/Makefile
@@ -1,6 +1,6 @@
CFLAGS += -g -I../../../../usr/include/

-TEST_GEN_PROGS := pidfd_test
+TEST_GEN_PROGS := pidfd_test pidfd_open_test

include ../lib.mk

diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
new file mode 100644
index 000000000000..8452e910463f
--- /dev/null
+++ b/tools/testing/selftests/pidfd/pidfd.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __PIDFD_H
+#define __PIDFD_H
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <sys/mount.h>
+
+#include "../kselftest.h"
+
+/*
+ * 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
+
+/*
+ * 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
+
+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 (!WIFEXITED(status))
+ return -1;
+
+ return WEXITSTATUS(status);
+}
+
+
+#endif /* __PIDFD_H */
diff --git a/tools/testing/selftests/pidfd/pidfd_open_test.c b/tools/testing/selftests/pidfd/pidfd_open_test.c
new file mode 100644
index 000000000000..ebe7a96cc8d6
--- /dev/null
+++ b/tools/testing/selftests/pidfd/pidfd_open_test.c
@@ -0,0 +1,361 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+#include <sched.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <syscall.h>
+#include <sys/mount.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "pidfd.h"
+#include "../kselftest.h"
+
+static inline int sys_pidfd_open(pid_t pid, unsigned int flags)
+{
+ return syscall(__NR_pidfd_open, pid, flags);
+}
+
+static int safe_int(const char *numstr, int *converted)
+{
+ char *err = NULL;
+ signed long int 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;
+}
+
+static pid_t get_pid_from_status_file(int *fd, const char *key, size_t keylen)
+{
+ int ret;
+ FILE *f;
+ size_t n = 0;
+ pid_t result = -1;
+ char *line = NULL;
+
+ /* fd now belongs to FILE and will be closed by fclose() */
+ f = fdopen(*fd, "r");
+ 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);
+ *fd = -1;
+ return result;
+}
+
+static int set_ns_last_pid(void)
+{
+ int fd;
+ ssize_t bytes;
+
+ fd = open("/proc/sys/kernel/ns_last_pid", O_WRONLY | O_CLOEXEC);
+ if (fd < 0) {
+ ksft_print_msg("failed to open \"/proc/sys/kernel/ns_last_pid\"n");
+ return -1;
+ }
+
+ bytes = write(fd, "999", sizeof("999") - 1);
+ close(fd);
+ if (bytes < 0 || (size_t)bytes != (sizeof("999") - 1))
+ return -1;
+
+ return 0;
+}
+
+static int test_pidfd_to_procfd_recycled_pid_fail(void)
+{
+ const char *test_name = "pidfd_open pidfd to procfd conversion on pid recycling";
+ int ret;
+ pid_t pid1;
+
+ 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);
+
+ /*
+ * This is lazy with file descriptor closing in the child process but
+ * it doesn't matter since we are very short-lived anyway and the
+ * cleanup would just be more complexity in this test.
+ */
+ if (pid1 == 0) {
+ int pidfd, procpidfd, procfd, ret;
+ pid_t pid2;
+
+
+ (void)umount2("/proc", MNT_DETACH);
+ ret = mount("proc", "/proc", "proc", 0, NULL);
+ if (ret < 0) {
+ ksft_print_msg("failed to mount a fresh /proc instance\n");
+ _exit(PIDFD_ERROR);
+ }
+
+ /* get pidfd for pid 1000 */
+ if (set_ns_last_pid() < 0) {
+ ksft_print_msg("failed to set ns_last_pid\n");
+ _exit(PIDFD_ERROR);
+ }
+
+ pid2 = fork();
+ if (pid2 < 0) {
+ ksft_print_msg("failed to create new process\n");
+ _exit(PIDFD_ERROR);
+ }
+
+ if (pid2 == 0)
+ _exit(PIDFD_PASS);
+
+ if (pid2 == PID_RECYCLE) {
+ pidfd = sys_pidfd_open(pid2, 0);
+ } else {
+ ksft_print_msg("failed to create process with pid %d\n",
+ PID_RECYCLE);
+ _exit(PIDFD_ERROR);
+ }
+
+ if (wait_for_pid(pid2))
+ _exit(PIDFD_ERROR);
+
+ if (pidfd < 0)
+ _exit(PIDFD_ERROR);
+
+ /* recycle pid 1000 */
+ if (set_ns_last_pid() < 0) {
+ ksft_print_msg("failed to set ns_last_pid\n");
+ _exit(PIDFD_ERROR);
+ }
+
+ pid2 = fork();
+ if (pid2 < 0) {
+ ksft_print_msg("failed to create new process\n");
+ _exit(PIDFD_ERROR);
+ }
+
+ if (pid2 == 0)
+ _exit(PIDFD_PASS);
+
+ if (pid2 != PID_RECYCLE) {
+ ksft_print_msg("failed to recycle pid %d\n",
+ PID_RECYCLE);
+ _exit(PIDFD_ERROR);
+ }
+
+ /*
+ * Now PID_RECYCLE is in zombie state since we have not waited
+ * on it yet, but it might have already exited. This ensures
+ * that the /proc/<pid> directory stays around.
+ */
+ procfd = open("/proc", O_DIRECTORY | O_RDONLY | O_CLOEXEC);
+ if (procfd < 0) {
+ ksft_print_msg("%s - failed to open /proc\n",
+ strerror(errno));
+ _exit(PIDFD_ERROR);
+ }
+
+ procpidfd = ioctl(pidfd, PIDFD_GET_PROCFD, procfd);
+ if (procpidfd >= 0) {
+ ksft_print_msg(
+ "managed to get access to /proc/<pid> of recycled pid\n");
+ _exit(PIDFD_ERROR);
+ }
+
+ if (wait_for_pid(pid2))
+ _exit(PIDFD_ERROR);
+
+ _exit(PIDFD_PASS);
+ }
+
+ if (wait_for_pid(pid1) != 0)
+ return -1;
+
+ ksft_test_result_pass("%s test: passed\n", test_name);
+ ksft_inc_pass_cnt();
+ return 0;
+}
+
+int main(int argc, char **argv)
+{
+ int ret = 1;
+ int pidfd = -1, procfd = -1, procpidfd = -1, statusfd = -1;
+ pid_t pid;
+
+ pidfd = sys_pidfd_open(-1, 0);
+ if (pidfd >= 0) {
+ ksft_print_msg(
+ "%s - succeeded to open pidfd for invalid pid -1\n",
+ strerror(errno));
+ goto on_error;
+ }
+ ksft_test_result_pass("do not allow invalid pid test: passed\n");
+ ksft_inc_pass_cnt();
+
+ pidfd = sys_pidfd_open(getpid(), 1);
+ if (pidfd >= 0) {
+ ksft_print_msg(
+ "%s - succeeded to open pidfd with invalid flag value specified\n",
+ strerror(errno));
+ goto on_error;
+ }
+ ksft_test_result_pass("do not allow invalid flag test: passed\n");
+ ksft_inc_pass_cnt();
+
+ pidfd = sys_pidfd_open(getpid(), 0);
+ if (pidfd < 0) {
+ ksft_print_msg("%s - failed to open pidfd\n", strerror(errno));
+ goto on_error;
+ }
+ ksft_test_result_pass("open a new pidfd test: passed\n");
+ ksft_inc_pass_cnt();
+
+ procfd = open("/proc", O_DIRECTORY | O_RDONLY | O_CLOEXEC);
+ if (procfd < 0) {
+ ksft_print_msg("%s - failed to open /proc\n", strerror(errno));
+ goto on_error;
+ }
+
+ procpidfd = ioctl(pidfd, PIDFD_GET_PROCFD, procfd);
+ if (procpidfd < 0) {
+ ksft_print_msg(
+ "%s - failed to retrieve /proc/<pid> from pidfd\n",
+ strerror(errno));
+ goto on_error;
+ }
+
+ statusfd = openat(procpidfd, "status", O_CLOEXEC | O_RDONLY);
+ if (statusfd < 0) {
+ ksft_print_msg("%s - failed to open /proc/<pid>/status\n",
+ strerror(errno));
+ goto on_error;
+ }
+
+ pid = get_pid_from_status_file(&statusfd, "Pid:", sizeof("Pid:") - 1);
+ if (pid < 0) {
+ ksft_print_msg(
+ "%s - failed to retrieve pid from /proc/<pid>/status\n",
+ strerror(errno));
+ goto on_error;
+ }
+
+ if (pid != getpid()) {
+ ksft_print_msg(
+ "%s - actual pid %d does not equal retrieved pid from /proc/<pid>/status\n",
+ strerror(errno), pid, getpid());
+ goto on_error;
+ }
+ ksft_test_result_pass("convert pidfd to /proc/<pid> fd test: passed\n");
+ ksft_inc_pass_cnt();
+
+ ret = test_pidfd_to_procfd_recycled_pid_fail();
+
+on_error:
+ if (pidfd >= 0)
+ close(pidfd);
+
+ if (procfd >= 0)
+ close(procfd);
+
+ if (procpidfd >= 0)
+ close(procpidfd);
+
+ if (statusfd >= 0)
+ close(statusfd);
+
+ return !ret ? ksft_exit_pass() : ksft_exit_fail();
+}
diff --git a/tools/testing/selftests/pidfd/pidfd_test.c b/tools/testing/selftests/pidfd/pidfd_test.c
index d59378a93782..f01de87249c9 100644
--- a/tools/testing/selftests/pidfd/pidfd_test.c
+++ b/tools/testing/selftests/pidfd/pidfd_test.c
@@ -14,6 +14,7 @@
#include <sys/wait.h>
#include <unistd.h>

+#include "pidfd.h"
#include "../kselftest.h"

static inline int sys_pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
@@ -62,28 +63,6 @@ static int test_pidfd_send_signal_simple_success(void)
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;
@@ -128,13 +107,6 @@ static int test_pidfd_send_signal_exited_fail(void)
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
@@ -143,17 +115,6 @@ static int test_pidfd_send_signal_exited_fail(void)
*/
#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;
--
2.21.0

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