Unverified Commit 3f1724dd authored by Christian Brauner's avatar Christian Brauner
Browse files

selftests: create detached mounts from detached mounts 

Link: https://lore.kernel.org/r/20250221-brauner-open_tree-v1-7-dbcfcb98c676@kernel.org


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent c5c12f87

tools/testing/selftests/mount_setattr/mount_setattr_test.c

+283 −0
Original line number Diff line number Diff line
@@ -126,6 +126,26 @@ 
	#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 MOUNT_ATTR_IDMAP

#define MOUNT_ATTR_IDMAP 0x00100000

#endif
@@ -157,6 +177,51 @@ 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;
@@ -397,6 +462,10 @@ FIXTURE_SETUP(mount_setattr) 


	ASSERT_EQ(mkdir("/tmp/B/BB", 0777), 0);



	ASSERT_EQ(mkdir("/tmp/target1", 0777), 0);



	ASSERT_EQ(mkdir("/tmp/target2", 0777), 0);



	ASSERT_EQ(mount("testing", "/tmp/B/BB", "tmpfs", MS_NOATIME | MS_NODEV,

			"size=100000,mode=700"), 0);
@@ -1506,4 +1575,218 @@ TEST_F(mount_setattr, mount_attr_nosymfollow) 
	ASSERT_EQ(close(fd), 0);

}



TEST_F(mount_setattr, open_tree_detached)

{

	int fd_tree_base = -EBADF, fd_tree_subdir = -EBADF;

	struct statx stx;



	fd_tree_base = sys_open_tree(-EBADF, "/mnt",

				     AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |

				     AT_RECURSIVE | OPEN_TREE_CLOEXEC |

				     OPEN_TREE_CLONE);

	ASSERT_GE(fd_tree_base, 0);

	/*

	 * /mnt                   testing tmpfs

	 * |-/mnt/A               testing tmpfs

	 * | `-/mnt/A/AA          testing tmpfs

	 * |   `-/mnt/A/AA/B      testing tmpfs

	 * |     `-/mnt/A/AA/B/BB testing tmpfs

	 * `-/mnt/B               testing ramfs

	 */

	ASSERT_EQ(statx(fd_tree_base, "A", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA/B", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA/B/BB", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);



	fd_tree_subdir = sys_open_tree(fd_tree_base, "A/AA",

				       AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |

				       AT_RECURSIVE | OPEN_TREE_CLOEXEC |

				       OPEN_TREE_CLONE);

	ASSERT_GE(fd_tree_subdir, 0);

	/*

	 * /AA          testing tmpfs

	 * `-/AA/B      testing tmpfs

	 *   `-/AA/B/BB testing tmpfs

	 */

	ASSERT_EQ(statx(fd_tree_subdir, "B", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_subdir, "B/BB", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);



	ASSERT_EQ(move_mount(fd_tree_subdir, "", -EBADF, "/tmp/target1", MOVE_MOUNT_F_EMPTY_PATH), 0);

	/*

	 * /tmp/target1          testing tmpfs

	 * `-/tmp/target1/B      testing tmpfs

	 *   `-/tmp/target1/B/BB testing tmpfs

	 */

	ASSERT_EQ(statx(-EBADF, "/tmp/target1", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(-EBADF, "/tmp/target1/B", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(-EBADF, "/tmp/target1/B/BB", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);



	ASSERT_EQ(move_mount(fd_tree_base, "", -EBADF, "/tmp/target2", MOVE_MOUNT_F_EMPTY_PATH), 0);

	/*

	 * /tmp/target2                   testing tmpfs

	 * |-/tmp/target2/A               testing tmpfs

	 * | `-/tmp/target2/A/AA          testing tmpfs

	 * |   `-/tmp/target2/A/AA/B      testing tmpfs

	 * |     `-/tmp/target2/A/AA/B/BB testing tmpfs

	 * `-/tmp/target2/B               testing ramfs

	 */

	ASSERT_EQ(statx(-EBADF, "/tmp/target2", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(-EBADF, "/tmp/target2/A", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(-EBADF, "/tmp/target2/A/AA", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(-EBADF, "/tmp/target2/A/AA/B", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(-EBADF, "/tmp/target2/A/AA/B/BB", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(-EBADF, "/tmp/target2/B", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);



	EXPECT_EQ(close(fd_tree_base), 0);

	EXPECT_EQ(close(fd_tree_subdir), 0);

}



TEST_F(mount_setattr, open_tree_detached_fail)

{

	int fd_tree_base = -EBADF, fd_tree_subdir = -EBADF;

	struct statx stx;



	fd_tree_base = sys_open_tree(-EBADF, "/mnt",

				     AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |

				     AT_RECURSIVE | OPEN_TREE_CLOEXEC |

				     OPEN_TREE_CLONE);

	ASSERT_GE(fd_tree_base, 0);

	/*

	 * /mnt                   testing tmpfs

	 * |-/mnt/A               testing tmpfs

	 * | `-/mnt/A/AA          testing tmpfs

	 * |   `-/mnt/A/AA/B      testing tmpfs

	 * |     `-/mnt/A/AA/B/BB testing tmpfs

	 * `-/mnt/B               testing ramfs

	 */

	ASSERT_EQ(statx(fd_tree_base, "A", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA/B", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA/B/BB", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);



	ASSERT_EQ(unshare(CLONE_NEWNS), 0);



	/*

	 * The origin mount namespace of the anonymous mount namespace

	 * of @fd_tree_base doesn't match the caller's mount namespace

	 * anymore so creation of another detached mounts must fail.

	 */

	fd_tree_subdir = sys_open_tree(fd_tree_base, "A/AA",

				       AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |

				       AT_RECURSIVE | OPEN_TREE_CLOEXEC |

				       OPEN_TREE_CLONE);

	ASSERT_LT(fd_tree_subdir, 0);

	ASSERT_EQ(errno, EINVAL);

}



TEST_F(mount_setattr, open_tree_detached_fail2)

{

	int fd_tree_base = -EBADF, fd_tree_subdir = -EBADF;

	struct statx stx;



	fd_tree_base = sys_open_tree(-EBADF, "/mnt",

				     AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |

				     AT_RECURSIVE | OPEN_TREE_CLOEXEC |

				     OPEN_TREE_CLONE);

	ASSERT_GE(fd_tree_base, 0);

	/*

	 * /mnt                   testing tmpfs

	 * |-/mnt/A               testing tmpfs

	 * | `-/mnt/A/AA          testing tmpfs

	 * |   `-/mnt/A/AA/B      testing tmpfs

	 * |     `-/mnt/A/AA/B/BB testing tmpfs

	 * `-/mnt/B               testing ramfs

	 */

	ASSERT_EQ(statx(fd_tree_base, "A", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA/B", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA/B/BB", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);



	EXPECT_EQ(create_and_enter_userns(), 0);



	/*

	 * The caller entered a new user namespace. They will have

	 * CAP_SYS_ADMIN in this user namespace. However, they're still

	 * located in a mount namespace that is owned by an ancestor

	 * user namespace in which they hold no privilege. Creating a

	 * detached mount must thus fail.

	 */

	fd_tree_subdir = sys_open_tree(fd_tree_base, "A/AA",

				       AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |

				       AT_RECURSIVE | OPEN_TREE_CLOEXEC |

				       OPEN_TREE_CLONE);

	ASSERT_LT(fd_tree_subdir, 0);

	ASSERT_EQ(errno, EPERM);

}



TEST_F(mount_setattr, open_tree_detached_fail3)

{

	int fd_tree_base = -EBADF, fd_tree_subdir = -EBADF;

	struct statx stx;



	fd_tree_base = sys_open_tree(-EBADF, "/mnt",

				     AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |

				     AT_RECURSIVE | OPEN_TREE_CLOEXEC |

				     OPEN_TREE_CLONE);

	ASSERT_GE(fd_tree_base, 0);

	/*

        * /mnt                   testing tmpfs

        * |-/mnt/A               testing tmpfs

        * | `-/mnt/A/AA          testing tmpfs

        * |   `-/mnt/A/AA/B      testing tmpfs

        * |     `-/mnt/A/AA/B/BB testing tmpfs

        * `-/mnt/B               testing ramfs

        */

	ASSERT_EQ(statx(fd_tree_base, "A", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA/B", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);

	ASSERT_EQ(statx(fd_tree_base, "A/AA/B/BB", 0, 0, &stx), 0);

	ASSERT_TRUE(stx.stx_attributes & STATX_ATTR_MOUNT_ROOT);



	EXPECT_EQ(prepare_unpriv_mountns(), 0);



	/*

        * The caller entered a new mount namespace. They will have

        * CAP_SYS_ADMIN in the owning user namespace of their mount

        * namespace.

        *

        * However, the origin mount namespace of the anonymous mount

        * namespace of @fd_tree_base doesn't match the caller's mount

        * namespace anymore so creation of another detached mounts must

        * fail.

        */

	fd_tree_subdir = sys_open_tree(fd_tree_base, "A/AA",

			               AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW |

				       AT_RECURSIVE | OPEN_TREE_CLOEXEC |

				       OPEN_TREE_CLONE);

	ASSERT_LT(fd_tree_subdir, 0);

	ASSERT_EQ(errno, EINVAL);

}



TEST_HARNESS_MAIN