6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Günther Noack [ Upstream commit ee890889b30b22f9a21636061def7a04e4f89380 ] Add tests to check that whiteout object creation is guarded by LANDLOCK_ACCESS_FS_MAKE_REG, in the cases where these are created from userspace: * Conventional creation with mknod() * Linking or renaming an existing whiteout object * renameat2() with RENAME_WHITEOUT, which creates a new whiteout object in the source location * renameat2() with RENAME_EXCHANGE, with one of the renamed objects being a whiteout object Signed-off-by: Günther Noack Link: https://patch.msgid.link/20260813093157.1436894-4-gnoack@google.com [mic: Update commit message as requested] Signed-off-by: Mickaël Salaün [mic: Backport: adapt the tests to the older filesystem fixture and ruleset helper] Signed-off-by: Mickaël Salaün Signed-off-by: Sasha Levin --- tools/testing/selftests/landlock/fs_test.c | 209 ++++++++++++++++++++- 1 file changed, 207 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 29658ba7d6d9..b92597b8cd47 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -38,6 +38,10 @@ int renameat2(int olddirfd, const char *oldpath, int newdirfd, #define RENAME_EXCHANGE (1 << 1) #endif +#ifndef RENAME_WHITEOUT +#define RENAME_WHITEOUT (1 << 2) +#endif + #define TMP_DIR "tmp" #define BINARY_PATH "./true" @@ -65,6 +69,8 @@ static const char file1_s3d1[] = TMP_DIR "/s3d1/f1"; /* dir_s3d2 is a mount point. */ static const char dir_s3d2[] = TMP_DIR "/s3d1/s3d2"; static const char dir_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3"; +static const char file1_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3/f1"; +static const char file1_s3d4[] = TMP_DIR "/s3d1/s3d2/s3d4/f1"; /* * layout1 hierarchy: @@ -340,7 +346,8 @@ static void create_layout1(struct __test_metadata *const _metadata) ASSERT_EQ(0, mount_opt(&mnt_tmp, dir_s3d2)); clear_cap(_metadata, CAP_SYS_ADMIN); - ASSERT_EQ(0, mkdir(dir_s3d3, 0700)); + create_file(_metadata, file1_s3d3); + create_file(_metadata, file1_s3d4); } static void remove_layout1(struct __test_metadata *const _metadata) @@ -360,7 +367,8 @@ static void remove_layout1(struct __test_metadata *const _metadata) EXPECT_EQ(0, remove_path(dir_s2d2)); EXPECT_EQ(0, remove_path(file1_s3d1)); - EXPECT_EQ(0, remove_path(dir_s3d3)); + EXPECT_EQ(0, remove_path(file1_s3d3)); + EXPECT_EQ(0, remove_path(file1_s3d4)); set_cap(_metadata, CAP_SYS_ADMIN); umount(dir_s3d2); clear_cap(_metadata, CAP_SYS_ADMIN); @@ -702,6 +710,27 @@ static void enforce_ruleset(struct __test_metadata *const _metadata, } } +static void enforce_fs(struct __test_metadata *const _metadata, + const __u64 access_fs, const struct rule rules[]) +{ + int ruleset_fd; + + if (rules) { + ruleset_fd = create_ruleset(_metadata, access_fs, rules); + } else { + const struct landlock_ruleset_attr ruleset_attr = { + .handled_access_fs = access_fs, + }; + + ruleset_fd = landlock_create_ruleset(&ruleset_attr, + sizeof(ruleset_attr), 0); + ASSERT_LE(0, ruleset_fd); + } + + enforce_ruleset(_metadata, ruleset_fd); + EXPECT_EQ(0, close(ruleset_fd)); +} + TEST_F_FORK(layout0, proc_nsfs) { const struct rule rules[] = { @@ -2078,6 +2107,170 @@ TEST_F_FORK(layout1, rename_file) RENAME_EXCHANGE)); } +TEST_F_FORK(layout1, rename_whiteout_denied) +{ + /* The affected file is a FIFO. */ + ASSERT_EQ(0, unlink(file1_s3d3)); + ASSERT_EQ(0, mknod(file1_s3d3, S_IFIFO | 0600, 0)); + + /* Deny MAKE_REG, but allow MAKE_FIFO. */ + enforce_fs(_metadata, LANDLOCK_ACCESS_FS_MAKE_REG, NULL); + + /* + * Try to rename a file with RENAME_WHITEOUT. + * file1_s3d3 is in dir_s3d2 (tmpfs), so it supports RENAME_WHITEOUT. + * Denied, because whiteout creation is guarded with MAKE_REG. + */ + EXPECT_EQ(-1, renameat2(AT_FDCWD, file1_s3d3, AT_FDCWD, + TMP_DIR "/s3d1/s3d2/s3d3/f2", RENAME_WHITEOUT)); + EXPECT_EQ(EACCES, errno); +} + +static bool is_whiteout(const char *const path) +{ + struct stat st; + + if (stat(path, &st) == -1) + return false; + + return S_ISCHR(st.st_mode) && st.st_rdev == makedev(0, 0); +} + +static bool is_fifo(const char *const path) +{ + struct stat st; + + return stat(path, &st) == 0 && S_ISFIFO(st.st_mode); +} + +TEST_F_FORK(layout1, rename_whiteout_allowed) +{ + const struct rule rules[] = { + { + .path = dir_s3d3, + .access = LANDLOCK_ACCESS_FS_MAKE_REG, + }, + {}, + }; + + /* The affected file is a FIFO. */ + ASSERT_EQ(0, unlink(file1_s3d3)); + ASSERT_EQ(0, mknod(file1_s3d3, S_IFIFO | 0600, 0)); + + /* Allow MAKE_REG below dir_s3d3. */ + enforce_fs(_metadata, LANDLOCK_ACCESS_FS_MAKE_REG, rules); + + /* + * Rename a file with RENAME_WHITEOUT within the same directory. + * Allowed, because MAKE_REG is granted for the whiteout object which + * gets created in the source location. + */ + EXPECT_EQ(0, renameat2(AT_FDCWD, file1_s3d3, AT_FDCWD, + TMP_DIR "/s3d1/s3d2/s3d3/f2", RENAME_WHITEOUT)); + + /* A whiteout object took the place of the moved FIFO. */ + EXPECT_TRUE(is_whiteout(file1_s3d3)); + EXPECT_TRUE(is_fifo(TMP_DIR "/s3d1/s3d2/s3d3/f2")); +} + +TEST_F_FORK(layout1, rename_whiteout_reparenting) +{ + const struct rule rules[] = { + { + .path = dir_s3d2, + .access = LANDLOCK_ACCESS_FS_REFER, + }, + { + .path = dir_s3d3, + .access = LANDLOCK_ACCESS_FS_MAKE_REG, + }, + {}, + }; + + /* The moved files are FIFOs. */ + ASSERT_EQ(0, unlink(file1_s3d3)); + ASSERT_EQ(0, mknod(file1_s3d3, S_IFIFO | 0600, 0)); + ASSERT_EQ(0, unlink(file1_s3d4)); + ASSERT_EQ(0, mknod(file1_s3d4, S_IFIFO | 0600, 0)); + + /* Allow REFER below dir_s3d2, but MAKE_REG only below dir_s3d3. */ + enforce_fs(_metadata, + LANDLOCK_ACCESS_FS_MAKE_REG | LANDLOCK_ACCESS_FS_REFER, + rules); + + /* + * The whiteout object is created in the source directory: Moving the + * FIFO out of dir_s3d4 is denied because MAKE_REG is not granted + * there, even though it is granted in the destination directory + * dir_s3d3. + */ + EXPECT_EQ(-1, renameat2(AT_FDCWD, file1_s3d4, AT_FDCWD, + TMP_DIR "/s3d1/s3d2/s3d3/f2", RENAME_WHITEOUT)); + EXPECT_EQ(EACCES, errno); + + /* + * Moving the FIFO out of dir_s3d3 is allowed, because MAKE_REG is + * granted there for the created whiteout object. + */ + EXPECT_EQ(0, renameat2(AT_FDCWD, file1_s3d3, AT_FDCWD, + TMP_DIR "/s3d1/s3d2/s3d4/f2", RENAME_WHITEOUT)); + + /* A whiteout object took the place of the moved FIFO. */ + EXPECT_TRUE(is_whiteout(file1_s3d3)); + EXPECT_TRUE(is_fifo(TMP_DIR "/s3d1/s3d2/s3d4/f2")); +} + +TEST_F_FORK(layout1, rename_whiteout_exchange) +{ + const char *const whiteout_s3d3 = TMP_DIR "/s3d1/s3d2/s3d3/f2"; + const struct rule rules[] = { + { + .path = dir_s3d2, + .access = LANDLOCK_ACCESS_FS_REFER, + }, + { + .path = dir_s3d3, + .access = LANDLOCK_ACCESS_FS_MAKE_REG, + }, + {}, + }; + + /* The exchanged files are FIFOs and an existing whiteout object. */ + ASSERT_EQ(0, unlink(file1_s3d3)); + ASSERT_EQ(0, mknod(file1_s3d3, S_IFIFO | 0600, 0)); + ASSERT_EQ(0, mknod(whiteout_s3d3, S_IFCHR | 0600, makedev(0, 0))); + ASSERT_EQ(0, unlink(file1_s3d4)); + ASSERT_EQ(0, mknod(file1_s3d4, S_IFIFO | 0600, 0)); + + /* Allow REFER below dir_s3d2, but MAKE_REG only below dir_s3d3. */ + enforce_fs(_metadata, + LANDLOCK_ACCESS_FS_MAKE_REG | LANDLOCK_ACCESS_FS_REFER, + rules); + + /* + * With RENAME_EXCHANGE, the whiteout object moves into the source + * directory of the rename: Exchanging the FIFO in dir_s3d4 with the + * whiteout object is denied because MAKE_REG is not granted in + * dir_s3d4, even though it is granted in the whiteout object's own + * directory dir_s3d3. + */ + EXPECT_EQ(-1, renameat2(AT_FDCWD, file1_s3d4, AT_FDCWD, whiteout_s3d3, + RENAME_EXCHANGE)); + EXPECT_EQ(EACCES, errno); + + /* + * Exchanging the FIFO in dir_s3d3 with the whiteout object is + * allowed, because MAKE_REG is granted in the directory into which + * the whiteout object moves. + */ + EXPECT_EQ(0, renameat2(AT_FDCWD, file1_s3d3, AT_FDCWD, whiteout_s3d3, + RENAME_EXCHANGE)); + + /* The FIFO and the whiteout object swapped places. */ + EXPECT_TRUE(is_whiteout(file1_s3d3)); + EXPECT_TRUE(is_fifo(whiteout_s3d3)); +} + TEST_F_FORK(layout1, rename_dir) { const struct rule rules[] = { @@ -3094,6 +3287,18 @@ TEST_F_FORK(layout1, make_char) makedev(1, 3)); } +TEST_F_FORK(layout1, make_whiteout) +{ + /* + * Creates a whiteout object (creation guarded by MAKE_REG). + * + * Contrary to the other character devices, this does not require + * CAP_MKNOD, cf. vfs_mknod(). + */ + test_make_file(_metadata, LANDLOCK_ACCESS_FS_MAKE_REG, S_IFCHR, + makedev(0, 0)); +} + TEST_F_FORK(layout1, make_block) { /* Creates a /dev/loop0 device. */ -- 2.51.0