tests/pid_namespace: add pid_max tests

Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Link: https://lore.kernel.org/r/20241122132459.135120-3-aleksandr.mikhalitsyn@canonical.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/pid_namespace/.gitignore b/tools/testing/selftests/pid_namespace/.gitignore
index 93ab9d7e5b7ee2b876861a5b4dabb60311779104..5118f0f3edf4e737130fa0395ad957fbb8ae4671 100644 (file)
--- a/tools/testing/selftests/pid_namespace/.gitignore
+++ b/tools/testing/selftests/pid_namespace/.gitignore
@@ -1 +1,2 @@
+pid_max
 regression_enomem

diff --git a/tools/testing/selftests/pid_namespace/Makefile b/tools/testing/selftests/pid_namespace/Makefile
index 9286a1d22cd3acd95da26203086c7324887e9ce8..b972f55d07aeddcd243413f978c6e37b16aad416 100644 (file)
--- a/tools/testing/selftests/pid_namespace/Makefile
+++ b/tools/testing/selftests/pid_namespace/Makefile
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 CFLAGS += -g $(KHDR_INCLUDES)
 
-TEST_GEN_PROGS = regression_enomem
+TEST_GEN_PROGS = regression_enomem pid_max
 
 LOCAL_HDRS += $(selfdir)/pidfd/pidfd.h
 

diff --git a/tools/testing/selftests/pid_namespace/pid_max.c b/tools/testing/selftests/pid_namespace/pid_max.c
new file mode 100644 (file)
index 0000000..51c414f
--- /dev/null
+++ b/tools/testing/selftests/pid_namespace/pid_max.c
@@ -0,0 +1,358 @@
+/* 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 "../kselftest_harness.h"
+#include "../pidfd/pidfd.h"
+
+#define __STACK_SIZE (8 * 1024 * 1024)
+static pid_t do_clone(int (*fn)(void *), void *arg, int flags)
+{
+       char *stack;
+       pid_t ret;
+
+       stack = malloc(__STACK_SIZE);
+       if (!stack)
+               return -ENOMEM;
+
+#ifdef __ia64__
+       ret = __clone2(fn, stack, __STACK_SIZE, flags | SIGCHLD, arg);
+#else
+       ret = clone(fn, stack + __STACK_SIZE, flags | SIGCHLD, arg);
+#endif
+       free(stack);
+       return ret;
+}
+
+static int pid_max_cb(void *data)
+{
+       int fd, ret;
+       pid_t pid;
+
+       ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to make rootfs private mount\n");
+               return -1;
+       }
+
+       umount2("/proc", MNT_DETACH);
+
+       ret = mount("proc", "/proc", "proc", 0, NULL);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to mount proc\n");
+               return -1;
+       }
+
+       fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
+       if (fd < 0) {
+               fprintf(stderr, "%m - Failed to open pid_max\n");
+               return -1;
+       }
+
+       ret = write(fd, "500", sizeof("500") - 1);
+       if (ret < 0) {
+               fprintf(stderr, "%m - Failed to write pid_max\n");
+               return -1;
+       }
+
+       for (int i = 0; i < 501; i++) {
+               pid = fork();
+               if (pid == 0)
+                       exit(EXIT_SUCCESS);
+               wait_for_pid(pid);
+               if (pid > 500) {
+                       fprintf(stderr, "Managed to create pid number beyond limit\n");
+                       return -1;
+               }
+       }
+
+       return 0;
+}
+
+static int pid_max_nested_inner(void *data)
+{
+       int fret = -1;
+       pid_t pids[2];
+       int fd, i, ret;
+
+       ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to make rootfs private mount\n");
+               return fret;
+       }
+
+       umount2("/proc", MNT_DETACH);
+
+       ret = mount("proc", "/proc", "proc", 0, NULL);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to mount proc\n");
+               return fret;
+       }
+
+       fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
+       if (fd < 0) {
+               fprintf(stderr, "%m - Failed to open pid_max\n");
+               return fret;
+       }
+
+       ret = write(fd, "500", sizeof("500") - 1);
+       close(fd);
+       if (ret < 0) {
+               fprintf(stderr, "%m - Failed to write pid_max\n");
+               return fret;
+       }
+
+       pids[0] = fork();
+       if (pids[0] < 0) {
+               fprintf(stderr, "Failed to create first new process\n");
+               return fret;
+       }
+
+       if (pids[0] == 0)
+               exit(EXIT_SUCCESS);
+
+       pids[1] = fork();
+       wait_for_pid(pids[0]);
+       if (pids[1] >= 0) {
+               if (pids[1] == 0)
+                       exit(EXIT_SUCCESS);
+               wait_for_pid(pids[1]);
+
+               fprintf(stderr, "Managed to create process even though ancestor pid namespace had a limit\n");
+               return fret;
+       }
+
+       /* Now make sure that we wrap pids at 400. */
+       for (i = 0; i < 510; i++) {
+               pid_t pid;
+
+               pid = fork();
+               if (pid < 0)
+                       return fret;
+
+               if (pid == 0)
+                       exit(EXIT_SUCCESS);
+
+               wait_for_pid(pid);
+               if (pid >= 500) {
+                       fprintf(stderr, "Managed to create process with pid %d beyond configured limit\n", pid);
+                       return fret;
+               }
+       }
+
+       return 0;
+}
+
+static int pid_max_nested_outer(void *data)
+{
+       int fret = -1, nr_procs = 400;
+       pid_t pids[1000];
+       int fd, i, ret;
+       pid_t pid;
+
+       ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to make rootfs private mount\n");
+               return fret;
+       }
+
+       umount2("/proc", MNT_DETACH);
+
+       ret = mount("proc", "/proc", "proc", 0, NULL);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to mount proc\n");
+               return fret;
+       }
+
+       fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
+       if (fd < 0) {
+               fprintf(stderr, "%m - Failed to open pid_max\n");
+               return fret;
+       }
+
+       ret = write(fd, "400", sizeof("400") - 1);
+       close(fd);
+       if (ret < 0) {
+               fprintf(stderr, "%m - Failed to write pid_max\n");
+               return fret;
+       }
+
+       /*
+        * Create 397 processes. This leaves room for do_clone() (398) and
+        * one more 399. So creating another process needs to fail.
+        */
+       for (nr_procs = 0; nr_procs < 396; nr_procs++) {
+               pid = fork();
+               if (pid < 0)
+                       goto reap;
+
+               if (pid == 0)
+                       exit(EXIT_SUCCESS);
+
+               pids[nr_procs] = pid;
+       }
+
+       pid = do_clone(pid_max_nested_inner, NULL, CLONE_NEWPID | CLONE_NEWNS);
+       if (pid < 0) {
+               fprintf(stderr, "%m - Failed to clone nested pidns\n");
+               goto reap;
+       }
+
+       if (wait_for_pid(pid)) {
+               fprintf(stderr, "%m - Nested pid_max failed\n");
+               goto reap;
+       }
+
+       fret = 0;
+
+reap:
+       for (int i = 0; i < nr_procs; i++)
+               wait_for_pid(pids[i]);
+
+       return fret;
+}
+
+static int pid_max_nested_limit_inner(void *data)
+{
+       int fret = -1, nr_procs = 400;
+       int fd, ret;
+       pid_t pid;
+       pid_t pids[1000];
+
+       ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to make rootfs private mount\n");
+               return fret;
+       }
+
+       umount2("/proc", MNT_DETACH);
+
+       ret = mount("proc", "/proc", "proc", 0, NULL);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to mount proc\n");
+               return fret;
+       }
+
+       fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
+       if (fd < 0) {
+               fprintf(stderr, "%m - Failed to open pid_max\n");
+               return fret;
+       }
+
+       ret = write(fd, "500", sizeof("500") - 1);
+       close(fd);
+       if (ret < 0) {
+               fprintf(stderr, "%m - Failed to write pid_max\n");
+               return fret;
+       }
+
+       for (nr_procs = 0; nr_procs < 500; nr_procs++) {
+               pid = fork();
+               if (pid < 0)
+                       break;
+
+               if (pid == 0)
+                       exit(EXIT_SUCCESS);
+
+               pids[nr_procs] = pid;
+       }
+
+       if (nr_procs >= 400) {
+               fprintf(stderr, "Managed to create processes beyond the configured outer limit\n");
+               goto reap;
+       }
+
+       fret = 0;
+
+reap:
+       for (int i = 0; i < nr_procs; i++)
+               wait_for_pid(pids[i]);
+
+       return fret;
+}
+
+static int pid_max_nested_limit_outer(void *data)
+{
+       int fd, ret;
+       pid_t pid;
+
+       ret = mount("", "/", NULL, MS_PRIVATE | MS_REC, 0);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to make rootfs private mount\n");
+               return -1;
+       }
+
+       umount2("/proc", MNT_DETACH);
+
+       ret = mount("proc", "/proc", "proc", 0, NULL);
+       if (ret) {
+               fprintf(stderr, "%m - Failed to mount proc\n");
+               return -1;
+       }
+
+       fd = open("/proc/sys/kernel/pid_max", O_RDWR | O_CLOEXEC | O_NOCTTY);
+       if (fd < 0) {
+               fprintf(stderr, "%m - Failed to open pid_max\n");
+               return -1;
+       }
+
+       ret = write(fd, "400", sizeof("400") - 1);
+       close(fd);
+       if (ret < 0) {
+               fprintf(stderr, "%m - Failed to write pid_max\n");
+               return -1;
+       }
+
+       pid = do_clone(pid_max_nested_limit_inner, NULL, CLONE_NEWPID | CLONE_NEWNS);
+       if (pid < 0) {
+               fprintf(stderr, "%m - Failed to clone nested pidns\n");
+               return -1;
+       }
+
+       if (wait_for_pid(pid)) {
+               fprintf(stderr, "%m - Nested pid_max failed\n");
+               return -1;
+       }
+
+       return 0;
+}
+
+TEST(pid_max_simple)
+{
+       pid_t pid;
+
+
+       pid = do_clone(pid_max_cb, NULL, CLONE_NEWPID | CLONE_NEWNS);
+       ASSERT_GT(pid, 0);
+       ASSERT_EQ(0, wait_for_pid(pid));
+}
+
+TEST(pid_max_nested_limit)
+{
+       pid_t pid;
+
+       pid = do_clone(pid_max_nested_limit_outer, NULL, CLONE_NEWPID | CLONE_NEWNS);
+       ASSERT_GT(pid, 0);
+       ASSERT_EQ(0, wait_for_pid(pid));
+}
+
+TEST(pid_max_nested)
+{
+       pid_t pid;
+
+       pid = do_clone(pid_max_nested_outer, NULL, CLONE_NEWPID | CLONE_NEWNS);
+       ASSERT_GT(pid, 0);
+       ASSERT_EQ(0, wait_for_pid(pid));
+}
+
+TEST_HARNESS_MAIN