@@ -7,3 +7,4 @@ pidfd_fdinfo_test
pidfd_getfd_test
pidfd_setns_test
pidfd_file_handle_test
+pidfd_bind_mount
@@ -3,7 +3,7 @@ CFLAGS += -g $(KHDR_INCLUDES) -pthread -Wall
TEST_GEN_PROGS := pidfd_test pidfd_fdinfo_test pidfd_open_test \
pidfd_poll_test pidfd_wait pidfd_getfd_test pidfd_setns_test \
- pidfd_file_handle_test
+ pidfd_file_handle_test pidfd_bind_mount
include ../lib.mk
new file mode 100644
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// Copyright (c) 2024 Christian Brauner <brauner@kernel.org>
+
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <limits.h>
+#include <sched.h>
+#include <stdio.h>
+#include <string.h>
+#include <linux/fs.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/mount.h>
+#include <unistd.h>
+
+#include "pidfd.h"
+#include "../kselftest_harness.h"
+
+#ifndef __NR_open_tree
+ #if defined __alpha__
+ #define __NR_open_tree 538
+ #elif defined _MIPS_SIM
+ #if _MIPS_SIM == _MIPS_SIM_ABI32 /* o32 */
+ #define __NR_open_tree 4428
+ #endif
+ #if _MIPS_SIM == _MIPS_SIM_NABI32 /* n32 */
+ #define __NR_open_tree 6428
+ #endif
+ #if _MIPS_SIM == _MIPS_SIM_ABI64 /* n64 */
+ #define __NR_open_tree 5428
+ #endif
+ #elif defined __ia64__
+ #define __NR_open_tree (428 + 1024)
+ #else
+ #define __NR_open_tree 428
+ #endif
+#endif
+
+#ifndef __NR_move_mount
+ #if defined __alpha__
+ #define __NR_move_mount 539
+ #elif defined _MIPS_SIM
+ #if _MIPS_SIM == _MIPS_SIM_ABI32 /* o32 */
+ #define __NR_move_mount 4429
+ #endif
+ #if _MIPS_SIM == _MIPS_SIM_NABI32 /* n32 */
+ #define __NR_move_mount 6429
+ #endif
+ #if _MIPS_SIM == _MIPS_SIM_ABI64 /* n64 */
+ #define __NR_move_mount 5429
+ #endif
+ #elif defined __ia64__
+ #define __NR_move_mount (428 + 1024)
+ #else
+ #define __NR_move_mount 429
+ #endif
+#endif
+
+#ifndef MOVE_MOUNT_F_EMPTY_PATH
+#define MOVE_MOUNT_F_EMPTY_PATH 0x00000004 /* Empty from path permitted */
+#endif
+
+#ifndef MOVE_MOUNT_F_EMPTY_PATH
+#define MOVE_MOUNT_T_EMPTY_PATH 0x00000040 /* Empty to path permitted */
+#endif
+
+static inline int sys_move_mount(int from_dfd, const char *from_pathname,
+ int to_dfd, const char *to_pathname,
+ unsigned int flags)
+{
+ return syscall(__NR_move_mount, from_dfd, from_pathname, to_dfd,
+ to_pathname, flags);
+}
+
+#ifndef OPEN_TREE_CLONE
+#define OPEN_TREE_CLONE 1
+#endif
+
+#ifndef OPEN_TREE_CLOEXEC
+#define OPEN_TREE_CLOEXEC O_CLOEXEC
+#endif
+
+#ifndef AT_RECURSIVE
+#define AT_RECURSIVE 0x8000 /* Apply to the entire subtree */
+#endif
+
+static inline int sys_open_tree(int dfd, const char *filename, unsigned int flags)
+{
+ return syscall(__NR_open_tree, dfd, filename, flags);
+}
+
+FIXTURE(pidfd_bind_mount) {
+ char template[PATH_MAX];
+ int fd_tmp;
+ int pidfd;
+ struct stat st1;
+ struct stat st2;
+ __u32 gen1;
+ __u32 gen2;
+ bool must_unmount;
+};
+
+FIXTURE_SETUP(pidfd_bind_mount)
+{
+ self->fd_tmp = -EBADF;
+ self->must_unmount = false;
+ ASSERT_EQ(unshare(CLONE_NEWNS), 0);
+ ASSERT_LE(snprintf(self->template, PATH_MAX, "%s", P_tmpdir "/pidfd_bind_mount_XXXXXX"), PATH_MAX);
+ self->fd_tmp = mkstemp(self->template);
+ ASSERT_GE(self->fd_tmp, 0);
+ self->pidfd = sys_pidfd_open(getpid(), 0);
+ ASSERT_GE(self->pidfd, 0);
+ ASSERT_GE(fstat(self->pidfd, &self->st1), 0);
+ ASSERT_EQ(ioctl(self->pidfd, FS_IOC_GETVERSION, &self->gen1), 0);
+}
+
+FIXTURE_TEARDOWN(pidfd_bind_mount)
+{
+ ASSERT_EQ(close(self->fd_tmp), 0);
+ if (self->must_unmount)
+ ASSERT_EQ(umount2(self->template, 0), 0);
+ ASSERT_EQ(unlink(self->template), 0);
+}
+
+/*
+ * Test that a detached mount can be created for a pidfd and then
+ * attached to the filesystem hierarchy.
+ */
+TEST_F(pidfd_bind_mount, bind_mount)
+{
+ int fd_tree;
+
+ fd_tree = sys_open_tree(self->pidfd, "", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC | AT_EMPTY_PATH);
+ ASSERT_GE(fd_tree, 0);
+
+ ASSERT_EQ(move_mount(fd_tree, "", self->fd_tmp, "", MOVE_MOUNT_F_EMPTY_PATH | MOVE_MOUNT_T_EMPTY_PATH), 0);
+ self->must_unmount = true;
+
+ ASSERT_EQ(close(fd_tree), 0);
+}
+
+/* Test that a pidfd can be reopened through procfs. */
+TEST_F(pidfd_bind_mount, reopen)
+{
+ int pidfd;
+ char proc_path[PATH_MAX];
+
+ sprintf(proc_path, "/proc/self/fd/%d", self->pidfd);
+ pidfd = open(proc_path, O_RDONLY | O_NOCTTY | O_CLOEXEC);
+ ASSERT_GE(pidfd, 0);
+
+ ASSERT_GE(fstat(self->pidfd, &self->st2), 0);
+ ASSERT_EQ(ioctl(self->pidfd, FS_IOC_GETVERSION, &self->gen2), 0);
+
+ ASSERT_TRUE(self->st1.st_dev == self->st2.st_dev && self->st1.st_ino == self->st2.st_ino);
+ ASSERT_TRUE(self->gen1 == self->gen2);
+
+ ASSERT_EQ(close(pidfd), 0);
+}
+
+/*
+ * Test that a detached mount can be created for a pidfd and then
+ * attached to the filesystem hierarchy and reopened.
+ */
+TEST_F(pidfd_bind_mount, bind_mount_reopen)
+{
+ int fd_tree, fd_pidfd_mnt;
+
+ fd_tree = sys_open_tree(self->pidfd, "", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC | AT_EMPTY_PATH);
+ ASSERT_GE(fd_tree, 0);
+
+ ASSERT_EQ(move_mount(fd_tree, "", self->fd_tmp, "", MOVE_MOUNT_F_EMPTY_PATH | MOVE_MOUNT_T_EMPTY_PATH), 0);
+ self->must_unmount = true;
+
+ fd_pidfd_mnt = openat(-EBADF, self->template, O_RDONLY | O_NOCTTY | O_CLOEXEC);
+ ASSERT_GE(fd_pidfd_mnt, 0);
+
+ ASSERT_GE(fstat(fd_tree, &self->st2), 0);
+ ASSERT_EQ(ioctl(fd_pidfd_mnt, FS_IOC_GETVERSION, &self->gen2), 0);
+
+ ASSERT_TRUE(self->st1.st_dev == self->st2.st_dev && self->st1.st_ino == self->st2.st_ino);
+ ASSERT_TRUE(self->gen1 == self->gen2);
+
+ ASSERT_EQ(close(fd_tree), 0);
+ ASSERT_EQ(close(fd_pidfd_mnt), 0);
+}
+
+TEST_HARNESS_MAIN
Signed-off-by: Christian Brauner <brauner@kernel.org> --- tools/testing/selftests/pidfd/.gitignore | 1 + tools/testing/selftests/pidfd/Makefile | 2 +- tools/testing/selftests/pidfd/pidfd_bind_mount.c | 188 +++++++++++++++++++++++ 3 files changed, 190 insertions(+), 1 deletion(-)