From: Christian Kellner christian@kellner.me

Add a test that checks that if pid namespaces are configured the fdinfo file of a pidfd contains an NSpid: entry containing the process id in the current and additionally all nested namespaces. In the case that a pidfd is from a pid namespace not in the same namespace hierarchy as the process accessing the fdinfo file, ensure the 'NSpid' shows 0 for that pidfd, analogous to the 'Pid' entry.

Signed-off-by: Christian Kellner christian@kellner.me --- Changes in v4: - Rework to test include a the situation where the fdinfo for a pidfd of a process in a sibling pid namespace is being read and ensure the NSpid field only contains one entry, being 0.

tools/testing/selftests/pidfd/Makefile | 2 +- .../selftests/pidfd/pidfd_fdinfo_test.c | 265 ++++++++++++++++++ 2 files changed, 266 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/pidfd/pidfd_fdinfo_test.c

diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile index 7550f08822a3..43db1b98e845 100644 --- a/tools/testing/selftests/pidfd/Makefile +++ b/tools/testing/selftests/pidfd/Makefile @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0-only CFLAGS += -g -I../../../../usr/include/ -pthread

-TEST_GEN_PROGS := pidfd_test pidfd_open_test pidfd_poll_test pidfd_wait +TEST_GEN_PROGS := pidfd_test pidfd_fdinfo_test pidfd_open_test pidfd_poll_test pidfd_wait

include ../lib.mk

diff --git a/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c b/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c new file mode 100644 index 000000000000..3721be994abd --- /dev/null +++ b/tools/testing/selftests/pidfd/pidfd_fdinfo_test.c @@ -0,0 +1,265 @@ +// SPDX-License-Identifier: GPL-2.0 + +#define _GNU_SOURCE +#include <assert.h> +#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/wait.h> + +#include "pidfd.h" +#include "../kselftest.h" + +struct error { + int code; + char msg[512]; +}; + +static int error_set(struct error *err, int code, const char *fmt, ...) +{ + va_list args; + int r; + + if (code == PIDFD_PASS || !err || err->code != PIDFD_PASS) + return code; + + err->code = code; + va_start(args, fmt); + r = vsnprintf(err->msg, sizeof(err->msg), fmt, args); + assert((size_t)r < sizeof(err->msg)); + va_end(args); + + return code; +} + +static void error_report(struct error *err, const char *test_name) +{ + switch (err->code) { + case PIDFD_ERROR: + ksft_exit_fail_msg("%s test: Fatal: %s\n", test_name, err->msg); + break; + + case PIDFD_FAIL: + /* will be: not ok %d # error %s test: %s */ + ksft_test_result_error("%s test: %s\n", test_name, err->msg); + break; + + case PIDFD_SKIP: + /* will be: not ok %d # SKIP %s test: %s */ + ksft_test_result_skip("%s test: %s\n", test_name, err->msg); + break; + + case PIDFD_XFAIL: + ksft_test_result_pass("%s test: Expected failure: %s\n", + test_name, err->msg); + break; + + case PIDFD_PASS: + ksft_test_result_pass("%s test: Passed\n"); + break; + + default: + ksft_exit_fail_msg("%s test: Unknown code: %d %s\n", + test_name, err->code, err->msg); + break; + } +} + +static inline int error_check(struct error *err, const char *test_name) +{ + /* In case of error we bail out and terminate the test program */ + if (err->code == PIDFD_ERROR) + error_report(err, test_name); + + return err->code; +} + +struct child { + pid_t pid; + int fd; +}; + +static struct child clone_newns(int (*fn)(void *), void *args, + struct error *err) +{ + static int flags = CLONE_PIDFD | CLONE_NEWPID | CLONE_NEWNS | SIGCHLD; + size_t stack_size = 1024; + char *stack[1024] = { 0 }; + struct child ret; + + if (!(flags & CLONE_NEWUSER) && geteuid() != 0) + flags |= CLONE_NEWUSER; + +#ifdef __ia64__ + ret.pid = __clone2(fn, stack, stack_size, flags, args, &ret.fd); +#else + ret.pid = clone(fn, stack + stack_size, flags, args, &ret.fd); +#endif + + if (ret.pid < 0) { + error_set(err, PIDFD_ERROR, "clone failed (ret %d, errno %d)", + ret.fd, errno); + return ret; + } + + ksft_print_msg("New child: %d, fd: %d\n", ret.pid, ret.fd); + + return ret; +} + +static inline int child_join(struct child *child, struct error *err) +{ + int r; + + (void)close(child->fd); + r = wait_for_pid(child->pid); + if (r < 0) + error_set(err, PIDFD_ERROR, "waitpid failed (ret %d, errno %d)", + r, errno); + else if (r > 0) + error_set(err, r, "child %d reported: %d", child->pid, r); + + return r; +} + +static inline void trim_newline(char *str) +{ + char *pos = strrchr(str, '\n'); + + if (pos) + *pos = '\0'; +} + +static int verify_fdinfo_nspid(int pidfd, struct error *err, + const char *expect, ...) +{ + char buffer[512] = {0, }; + char path[512] = {0, }; + va_list args; + FILE *f; + char *line = NULL; + size_t n = 0; + int found = 0; + int r; + + va_start(args, expect); + r = vsnprintf(buffer, sizeof(buffer), expect, args); + assert((size_t)r < sizeof(buffer)); + va_end(args); + + snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", pidfd); + f = fopen(path, "re"); + if (!f) + return error_set(err, PIDFD_ERROR, "fdinfo open failed for %d", + pidfd); + + while (getline(&line, &n, f) != -1) { + if (strncmp(line, "NSpid:", 6)) + continue; + + found = 1; + + r = strcmp(line + 6, buffer); + if (r != 0) { + trim_newline(line); + trim_newline(buffer); + error_set(err, PIDFD_FAIL, "NSpid: '%s' != '%s'", + line + 6, buffer); + } + break; + } + + free(line); + fclose(f); + + if (found == 0) + return error_set(err, PIDFD_FAIL, "NSpid not found for fd %d", + pidfd); + + return PIDFD_PASS; +} + +static int child_fdinfo_nspid_test(void *args) +{ + struct error err; + int pidfd; + int r; + + /* if we got no fd for the sibling, we are done */ + if (!args) + return PIDFD_PASS; + + /* verify that we can not resolve the pidfd for a process + * in a sibling pid namespace, i.e. a pid namespace it is + * not in our or a descended namespace + */ + r = mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0); + if (r < 0) { + ksft_print_msg("Failed to remount / private\n"); + return PIDFD_ERROR; + } + + (void)umount2("/proc", MNT_DETACH); + r = mount("proc", "/proc", "proc", 0, NULL); + if (r < 0) { + ksft_print_msg("Failed to remount /proc\n"); + return PIDFD_ERROR; + } + + pidfd = *(int *)args; + r = verify_fdinfo_nspid(pidfd, &err, "\t0\n"); + + if (r != PIDFD_PASS) + ksft_print_msg("NSpid fdinfo check failed: %s\n", err.msg); + + return r; +} + +static void test_pidfd_fdinfo_nspid(void) +{ + struct child a, b; + struct error err = {0, }; + const char *test_name = "pidfd check for NSpid in fdinfo"; + + /* Create a new child in a new pid and mount namespace */ + a = clone_newns(child_fdinfo_nspid_test, NULL, &err); + error_check(&err, test_name); + + /* Pass the pidfd representing the first child to the + * second child, which will be in a sibling pid namespace, + * which means that the fdinfo NSpid entry for the pidfd + * should only contain '0'. + */ + b = clone_newns(child_fdinfo_nspid_test, &a.fd, &err); + error_check(&err, test_name); + + /* The children will have pid 1 in the new pid namespace, + * so the line must be 'NSPid:\t<pid>\t1'. + */ + verify_fdinfo_nspid(a.fd, &err, "\t%d\t%d\n", a.pid, 1); + verify_fdinfo_nspid(b.fd, &err, "\t%d\t%d\n", b.pid, 1); + + /* wait for the process, check the exit status and set + * 'err' accordingly, if it is not already set. + */ + child_join(&a, &err); + child_join(&b, &err); + + error_report(&err, test_name); +} + +int main(int argc, char **argv) +{ + ksft_print_header(); + ksft_set_plan(1); + + test_pidfd_fdinfo_nspid(); + + return ksft_exit_pass(); +}