Unverified Commit e5c10b19 authored by Christian Brauner's avatar Christian Brauner
Browse files

selftests: test subdirectory mounting 

This tests mounting a subdirectory without ever having to expose the
filesystem to a non-anonymous mount namespace.

Link: https://lore.kernel.org/r/20250225-work-mount-propagation-v1-3-e6e3724500eb@kernel.org


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 12e40cbb

tools/testing/selftests/mount_setattr/mount_setattr_test.c

+36 −45
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <stdarg.h>

#include <linux/mount.h>



#include "../filesystems/overlayfs/wrappers.h"

#include "../kselftest_harness.h"



#ifndef CLONE_NEWNS
@@ -177,51 +178,6 @@ static inline int sys_open_tree(int dfd, const char *filename, unsigned int flag 
	return syscall(__NR_open_tree, dfd, filename, flags);

}



/* move_mount() flags */

#ifndef MOVE_MOUNT_F_SYMLINKS

#define MOVE_MOUNT_F_SYMLINKS 0x00000001 /* Follow symlinks on from path */

#endif



#ifndef MOVE_MOUNT_F_AUTOMOUNTS

#define MOVE_MOUNT_F_AUTOMOUNTS 0x00000002 /* Follow automounts on from path */

#endif



#ifndef MOVE_MOUNT_F_EMPTY_PATH

#define MOVE_MOUNT_F_EMPTY_PATH 0x00000004 /* Empty from path permitted */

#endif



#ifndef MOVE_MOUNT_T_SYMLINKS

#define MOVE_MOUNT_T_SYMLINKS 0x00000010 /* Follow symlinks on to path */

#endif



#ifndef MOVE_MOUNT_T_AUTOMOUNTS

#define MOVE_MOUNT_T_AUTOMOUNTS 0x00000020 /* Follow automounts on to path */

#endif



#ifndef MOVE_MOUNT_T_EMPTY_PATH

#define MOVE_MOUNT_T_EMPTY_PATH 0x00000040 /* Empty to path permitted */

#endif



#ifndef MOVE_MOUNT_SET_GROUP

#define MOVE_MOUNT_SET_GROUP 0x00000100 /* Set sharing group instead */

#endif



#ifndef MOVE_MOUNT_BENEATH

#define MOVE_MOUNT_BENEATH 0x00000200 /* Mount beneath top mount */

#endif



#ifndef MOVE_MOUNT__MASK

#define MOVE_MOUNT__MASK 0x00000377

#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);

}



static ssize_t write_nointr(int fd, const void *buf, size_t count)

{

	ssize_t ret;
@@ -1789,6 +1745,41 @@ TEST_F(mount_setattr, open_tree_detached_fail3) 
	ASSERT_EQ(errno, EINVAL);

}



TEST_F(mount_setattr, open_tree_subfolder)

{

	int fd_context, fd_tmpfs, fd_tree;



	fd_context = sys_fsopen("tmpfs", 0);

	ASSERT_GE(fd_context, 0);



	ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_CMD_CREATE, NULL, NULL, 0), 0);



	fd_tmpfs = sys_fsmount(fd_context, 0, 0);

	ASSERT_GE(fd_tmpfs, 0);



	EXPECT_EQ(close(fd_context), 0);



	ASSERT_EQ(mkdirat(fd_tmpfs, "subdir", 0755), 0);



	fd_tree = sys_open_tree(fd_tmpfs, "subdir",

				AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |

				AT_RECURSIVE | OPEN_TREE_CLOEXEC |

				OPEN_TREE_CLONE);

	ASSERT_GE(fd_tree, 0);



	EXPECT_EQ(close(fd_tmpfs), 0);



	ASSERT_EQ(mkdirat(-EBADF, "/mnt/open_tree_subfolder", 0755), 0);



	ASSERT_EQ(sys_move_mount(fd_tree, "", -EBADF, "/mnt/open_tree_subfolder", MOVE_MOUNT_F_EMPTY_PATH), 0);



	EXPECT_EQ(close(fd_tree), 0);



	ASSERT_EQ(umount2("/mnt/open_tree_subfolder", 0), 0);



	EXPECT_EQ(rmdir("/mnt/open_tree_subfolder"), 0);

}



TEST_F(mount_setattr, mount_detached_mount_on_detached_mount_then_close)

{

	int fd_tree_base = -EBADF, fd_tree_subdir = -EBADF;