From b9f5ce27c8f8be409d6afca9797a2da01e5cebbb Mon Sep 17 00:00:00 2001 From: Günther Noack Date: Tue, 18 Oct 2022 20:22:09 +0200 Subject: landlock: Support file truncation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Introduce the LANDLOCK_ACCESS_FS_TRUNCATE flag for file truncation. This flag hooks into the path_truncate, file_truncate and file_alloc_security LSM hooks and covers file truncation using truncate(2), ftruncate(2), open(2) with O_TRUNC, as well as creat(). This change also increments the Landlock ABI version, updates corresponding selftests, and updates code documentation to document the flag. In security/security.c, allocate security blobs at pointer-aligned offsets. This fixes the problem where one LSM's security blob can shift another LSM's security blob to an unaligned address (reported by Nathan Chancellor). The following operations are restricted: open(2): requires the LANDLOCK_ACCESS_FS_TRUNCATE right if a file gets implicitly truncated as part of the open() (e.g. using O_TRUNC). Notable special cases: * open(..., O_RDONLY|O_TRUNC) can truncate files as well in Linux * open() with O_TRUNC does *not* need the TRUNCATE right when it creates a new file. truncate(2) (on a path): requires the LANDLOCK_ACCESS_FS_TRUNCATE right. ftruncate(2) (on a file): requires that the file had the TRUNCATE right when it was previously opened. File descriptors acquired by other means than open(2) (e.g. memfd_create(2)) continue to support truncation with ftruncate(2). Cc: Nathan Chancellor Signed-off-by: Günther Noack Acked-by: Paul Moore (LSM) Link: https://lore.kernel.org/r/20221018182216.301684-5-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/base_test.c | 2 +- tools/testing/selftests/landlock/fs_test.c | 7 ++++--- 2 files changed, 5 insertions(+), 4 deletions(-) (limited to 'tools/testing') diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c index da9290817866..72cdae277b02 100644 --- a/tools/testing/selftests/landlock/base_test.c +++ b/tools/testing/selftests/landlock/base_test.c @@ -75,7 +75,7 @@ TEST(abi_version) const struct landlock_ruleset_attr ruleset_attr = { .handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE, }; - ASSERT_EQ(2, landlock_create_ruleset(NULL, 0, + ASSERT_EQ(3, landlock_create_ruleset(NULL, 0, LANDLOCK_CREATE_RULESET_VERSION)); ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0, diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 45de42a027c5..87b28d14a1aa 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -406,9 +406,10 @@ TEST_F_FORK(layout1, inval) #define ACCESS_FILE ( \ LANDLOCK_ACCESS_FS_EXECUTE | \ LANDLOCK_ACCESS_FS_WRITE_FILE | \ - LANDLOCK_ACCESS_FS_READ_FILE) + LANDLOCK_ACCESS_FS_READ_FILE | \ + LANDLOCK_ACCESS_FS_TRUNCATE) -#define ACCESS_LAST LANDLOCK_ACCESS_FS_REFER +#define ACCESS_LAST LANDLOCK_ACCESS_FS_TRUNCATE #define ACCESS_ALL ( \ ACCESS_FILE | \ @@ -422,7 +423,7 @@ TEST_F_FORK(layout1, inval) LANDLOCK_ACCESS_FS_MAKE_FIFO | \ LANDLOCK_ACCESS_FS_MAKE_BLOCK | \ LANDLOCK_ACCESS_FS_MAKE_SYM | \ - ACCESS_LAST) + LANDLOCK_ACCESS_FS_REFER) /* clang-format on */ -- cgit v1.2.3 From 225351abe34407421a5ee34896ccca92a0544b5e Mon Sep 17 00:00:00 2001 From: Günther Noack Date: Tue, 18 Oct 2022 20:22:10 +0200 Subject: selftests/landlock: Test file truncation support MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit These tests exercise the following truncation operations: * truncate() (truncate by path) * ftruncate() (truncate by file descriptor) * open with the O_TRUNC flag * special case: creat(), which is open with O_CREAT|O_WRONLY|O_TRUNC. in the following scenarios: * Files with read, write and truncate rights. * Files with read and truncate rights. * Files with the truncate right. * Files without the truncate right. In particular, the following scenarios are enforced with the test: * open() with O_TRUNC requires the truncate right, if it truncates a file. open() already checks security_path_truncate() in this case, and it required no additional check in the Landlock LSM's file_open hook. * creat() requires the truncate right when called with an existing filename. * creat() does *not* require the truncate right when it's creating a new file. * ftruncate() requires that the file was opened by a thread that had the truncate right for the file at the time of open(). (The rights are carried along with the opened file.) Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20221018182216.301684-6-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 287 +++++++++++++++++++++++++++++ 1 file changed, 287 insertions(+) (limited to 'tools/testing') diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 87b28d14a1aa..718543fd3dfc 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -58,6 +58,7 @@ static const char file1_s2d3[] = TMP_DIR "/s2d1/s2d2/s2d3/f1"; static const char file2_s2d3[] = TMP_DIR "/s2d1/s2d2/s2d3/f2"; static const char dir_s3d1[] = TMP_DIR "/s3d1"; +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"; @@ -83,6 +84,7 @@ static const char dir_s3d3[] = TMP_DIR "/s3d1/s3d2/s3d3"; * │   ├── f1 * │   └── f2 * └── s3d1 + *    ├── f1 * └── s3d2 * └── s3d3 */ @@ -208,6 +210,7 @@ static void create_layout1(struct __test_metadata *const _metadata) create_file(_metadata, file1_s2d3); create_file(_metadata, file2_s2d3); + create_file(_metadata, file1_s3d1); create_directory(_metadata, dir_s3d2); set_cap(_metadata, CAP_SYS_ADMIN); ASSERT_EQ(0, mount("tmp", dir_s3d2, "tmpfs", 0, "size=4m,mode=700")); @@ -230,6 +233,7 @@ static void remove_layout1(struct __test_metadata *const _metadata) EXPECT_EQ(0, remove_path(file1_s2d2)); EXPECT_EQ(0, remove_path(file1_s2d1)); + EXPECT_EQ(0, remove_path(file1_s3d1)); EXPECT_EQ(0, remove_path(dir_s3d3)); set_cap(_metadata, CAP_SYS_ADMIN); umount(dir_s3d2); @@ -3158,6 +3162,289 @@ TEST_F_FORK(layout1, proc_pipe) ASSERT_EQ(0, close(pipe_fds[1])); } +/* Invokes truncate(2) and returns its errno or 0. */ +static int test_truncate(const char *const path) +{ + if (truncate(path, 10) < 0) + return errno; + return 0; +} + +/* + * Invokes creat(2) and returns its errno or 0. + * Closes the opened file descriptor on success. + */ +static int test_creat(const char *const path) +{ + int fd = creat(path, 0600); + + if (fd < 0) + return errno; + + /* + * Mixing error codes from close(2) and creat(2) should not lead to any + * (access type) confusion for this test. + */ + if (close(fd) < 0) + return errno; + return 0; +} + +/* + * Exercises file truncation when it's not restricted, + * as it was the case before LANDLOCK_ACCESS_FS_TRUNCATE existed. + */ +TEST_F_FORK(layout1, truncate_unhandled) +{ + const char *const file_r = file1_s1d1; + const char *const file_w = file2_s1d1; + const char *const file_none = file1_s1d2; + const struct rule rules[] = { + { + .path = file_r, + .access = LANDLOCK_ACCESS_FS_READ_FILE, + }, + { + .path = file_w, + .access = LANDLOCK_ACCESS_FS_WRITE_FILE, + }, + /* Implicitly: No rights for file_none. */ + {}, + }; + + const __u64 handled = LANDLOCK_ACCESS_FS_READ_FILE | + LANDLOCK_ACCESS_FS_WRITE_FILE; + int ruleset_fd; + + /* Enable Landlock. */ + ruleset_fd = create_ruleset(_metadata, handled, rules); + + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + /* + * Checks read right: truncate and open with O_TRUNC work, unless the + * file is attempted to be opened for writing. + */ + EXPECT_EQ(0, test_truncate(file_r)); + EXPECT_EQ(0, test_open(file_r, O_RDONLY | O_TRUNC)); + EXPECT_EQ(EACCES, test_open(file_r, O_WRONLY | O_TRUNC)); + EXPECT_EQ(EACCES, test_creat(file_r)); + + /* + * Checks write right: truncate and open with O_TRUNC work, unless the + * file is attempted to be opened for reading. + */ + EXPECT_EQ(0, test_truncate(file_w)); + EXPECT_EQ(EACCES, test_open(file_w, O_RDONLY | O_TRUNC)); + EXPECT_EQ(0, test_open(file_w, O_WRONLY | O_TRUNC)); + EXPECT_EQ(0, test_creat(file_w)); + + /* + * Checks "no rights" case: truncate works but all open attempts fail, + * including creat. + */ + EXPECT_EQ(0, test_truncate(file_none)); + EXPECT_EQ(EACCES, test_open(file_none, O_RDONLY | O_TRUNC)); + EXPECT_EQ(EACCES, test_open(file_none, O_WRONLY | O_TRUNC)); + EXPECT_EQ(EACCES, test_creat(file_none)); +} + +TEST_F_FORK(layout1, truncate) +{ + const char *const file_rwt = file1_s1d1; + const char *const file_rw = file2_s1d1; + const char *const file_rt = file1_s1d2; + const char *const file_t = file2_s1d2; + const char *const file_none = file1_s1d3; + const char *const dir_t = dir_s2d1; + const char *const file_in_dir_t = file1_s2d1; + const char *const dir_w = dir_s3d1; + const char *const file_in_dir_w = file1_s3d1; + const struct rule rules[] = { + { + .path = file_rwt, + .access = LANDLOCK_ACCESS_FS_READ_FILE | + LANDLOCK_ACCESS_FS_WRITE_FILE | + LANDLOCK_ACCESS_FS_TRUNCATE, + }, + { + .path = file_rw, + .access = LANDLOCK_ACCESS_FS_READ_FILE | + LANDLOCK_ACCESS_FS_WRITE_FILE, + }, + { + .path = file_rt, + .access = LANDLOCK_ACCESS_FS_READ_FILE | + LANDLOCK_ACCESS_FS_TRUNCATE, + }, + { + .path = file_t, + .access = LANDLOCK_ACCESS_FS_TRUNCATE, + }, + /* Implicitly: No access rights for file_none. */ + { + .path = dir_t, + .access = LANDLOCK_ACCESS_FS_TRUNCATE, + }, + { + .path = dir_w, + .access = LANDLOCK_ACCESS_FS_WRITE_FILE, + }, + {}, + }; + const __u64 handled = LANDLOCK_ACCESS_FS_READ_FILE | + LANDLOCK_ACCESS_FS_WRITE_FILE | + LANDLOCK_ACCESS_FS_TRUNCATE; + int ruleset_fd; + + /* Enable Landlock. */ + ruleset_fd = create_ruleset(_metadata, handled, rules); + + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + /* Checks read, write and truncate rights: truncation works. */ + EXPECT_EQ(0, test_truncate(file_rwt)); + EXPECT_EQ(0, test_open(file_rwt, O_RDONLY | O_TRUNC)); + EXPECT_EQ(0, test_open(file_rwt, O_WRONLY | O_TRUNC)); + + /* Checks read and write rights: no truncate variant works. */ + EXPECT_EQ(EACCES, test_truncate(file_rw)); + EXPECT_EQ(EACCES, test_open(file_rw, O_RDONLY | O_TRUNC)); + EXPECT_EQ(EACCES, test_open(file_rw, O_WRONLY | O_TRUNC)); + + /* + * Checks read and truncate rights: truncation works. + * + * Note: Files can get truncated using open() even with O_RDONLY. + */ + EXPECT_EQ(0, test_truncate(file_rt)); + EXPECT_EQ(0, test_open(file_rt, O_RDONLY | O_TRUNC)); + EXPECT_EQ(EACCES, test_open(file_rt, O_WRONLY | O_TRUNC)); + + /* Checks truncate right: truncate works, but can't open file. */ + EXPECT_EQ(0, test_truncate(file_t)); + EXPECT_EQ(EACCES, test_open(file_t, O_RDONLY | O_TRUNC)); + EXPECT_EQ(EACCES, test_open(file_t, O_WRONLY | O_TRUNC)); + + /* Checks "no rights" case: No form of truncation works. */ + EXPECT_EQ(EACCES, test_truncate(file_none)); + EXPECT_EQ(EACCES, test_open(file_none, O_RDONLY | O_TRUNC)); + EXPECT_EQ(EACCES, test_open(file_none, O_WRONLY | O_TRUNC)); + + /* + * Checks truncate right on directory: truncate works on contained + * files. + */ + EXPECT_EQ(0, test_truncate(file_in_dir_t)); + EXPECT_EQ(EACCES, test_open(file_in_dir_t, O_RDONLY | O_TRUNC)); + EXPECT_EQ(EACCES, test_open(file_in_dir_t, O_WRONLY | O_TRUNC)); + + /* + * Checks creat in dir_w: This requires the truncate right when + * overwriting an existing file, but does not require it when the file + * is new. + */ + EXPECT_EQ(EACCES, test_creat(file_in_dir_w)); + + ASSERT_EQ(0, unlink(file_in_dir_w)); + EXPECT_EQ(0, test_creat(file_in_dir_w)); +} + +/* Invokes ftruncate(2) and returns its errno or 0. */ +static int test_ftruncate(int fd) +{ + if (ftruncate(fd, 10) < 0) + return errno; + return 0; +} + +TEST_F_FORK(layout1, ftruncate) +{ + /* + * This test opens a new file descriptor at different stages of + * Landlock restriction: + * + * without restriction: ftruncate works + * something else but truncate restricted: ftruncate works + * truncate restricted and permitted: ftruncate works + * truncate restricted and not permitted: ftruncate fails + * + * Whether this works or not is expected to depend on the time when the + * FD was opened, not to depend on the time when ftruncate() was + * called. + */ + const char *const path = file1_s1d1; + const __u64 handled1 = LANDLOCK_ACCESS_FS_READ_FILE | + LANDLOCK_ACCESS_FS_WRITE_FILE; + const struct rule layer1[] = { + { + .path = path, + .access = LANDLOCK_ACCESS_FS_WRITE_FILE, + }, + {}, + }; + const __u64 handled2 = LANDLOCK_ACCESS_FS_TRUNCATE; + const struct rule layer2[] = { + { + .path = path, + .access = LANDLOCK_ACCESS_FS_TRUNCATE, + }, + {}, + }; + const __u64 handled3 = LANDLOCK_ACCESS_FS_TRUNCATE | + LANDLOCK_ACCESS_FS_WRITE_FILE; + const struct rule layer3[] = { + { + .path = path, + .access = LANDLOCK_ACCESS_FS_WRITE_FILE, + }, + {}, + }; + int fd_layer0, fd_layer1, fd_layer2, fd_layer3, ruleset_fd; + + fd_layer0 = open(path, O_WRONLY); + EXPECT_EQ(0, test_ftruncate(fd_layer0)); + + ruleset_fd = create_ruleset(_metadata, handled1, layer1); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + fd_layer1 = open(path, O_WRONLY); + EXPECT_EQ(0, test_ftruncate(fd_layer0)); + EXPECT_EQ(0, test_ftruncate(fd_layer1)); + + ruleset_fd = create_ruleset(_metadata, handled2, layer2); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + fd_layer2 = open(path, O_WRONLY); + EXPECT_EQ(0, test_ftruncate(fd_layer0)); + EXPECT_EQ(0, test_ftruncate(fd_layer1)); + EXPECT_EQ(0, test_ftruncate(fd_layer2)); + + ruleset_fd = create_ruleset(_metadata, handled3, layer3); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + fd_layer3 = open(path, O_WRONLY); + EXPECT_EQ(0, test_ftruncate(fd_layer0)); + EXPECT_EQ(0, test_ftruncate(fd_layer1)); + EXPECT_EQ(0, test_ftruncate(fd_layer2)); + EXPECT_EQ(EACCES, test_ftruncate(fd_layer3)); + + ASSERT_EQ(0, close(fd_layer0)); + ASSERT_EQ(0, close(fd_layer1)); + ASSERT_EQ(0, close(fd_layer2)); + ASSERT_EQ(0, close(fd_layer3)); +} + /* clang-format off */ FIXTURE(layout1_bind) {}; /* clang-format on */ -- cgit v1.2.3 From 41729af28fb4b2c6581edcdfba19dd7fa81bf43c Mon Sep 17 00:00:00 2001 From: Günther Noack Date: Tue, 18 Oct 2022 20:22:11 +0200 Subject: selftests/landlock: Test open() and ftruncate() in multiple scenarios MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This test uses multiple fixture variants to exercise a broader set of scnenarios. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20221018182216.301684-7-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 96 ++++++++++++++++++++++++++++++ 1 file changed, 96 insertions(+) (limited to 'tools/testing') diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 718543fd3dfc..308f6f36e8c0 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -3445,6 +3445,102 @@ TEST_F_FORK(layout1, ftruncate) ASSERT_EQ(0, close(fd_layer3)); } +/* clang-format off */ +FIXTURE(ftruncate) {}; +/* clang-format on */ + +FIXTURE_SETUP(ftruncate) +{ + prepare_layout(_metadata); + create_file(_metadata, file1_s1d1); +} + +FIXTURE_TEARDOWN(ftruncate) +{ + EXPECT_EQ(0, remove_path(file1_s1d1)); + cleanup_layout(_metadata); +} + +FIXTURE_VARIANT(ftruncate) +{ + const __u64 handled; + const __u64 permitted; + const int expected_open_result; + const int expected_ftruncate_result; +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(ftruncate, w_w) { + /* clang-format on */ + .handled = LANDLOCK_ACCESS_FS_WRITE_FILE, + .permitted = LANDLOCK_ACCESS_FS_WRITE_FILE, + .expected_open_result = 0, + .expected_ftruncate_result = 0, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(ftruncate, t_t) { + /* clang-format on */ + .handled = LANDLOCK_ACCESS_FS_TRUNCATE, + .permitted = LANDLOCK_ACCESS_FS_TRUNCATE, + .expected_open_result = 0, + .expected_ftruncate_result = 0, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(ftruncate, wt_w) { + /* clang-format on */ + .handled = LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_TRUNCATE, + .permitted = LANDLOCK_ACCESS_FS_WRITE_FILE, + .expected_open_result = 0, + .expected_ftruncate_result = EACCES, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(ftruncate, wt_wt) { + /* clang-format on */ + .handled = LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_TRUNCATE, + .permitted = LANDLOCK_ACCESS_FS_WRITE_FILE | + LANDLOCK_ACCESS_FS_TRUNCATE, + .expected_open_result = 0, + .expected_ftruncate_result = 0, +}; + +/* clang-format off */ +FIXTURE_VARIANT_ADD(ftruncate, wt_t) { + /* clang-format on */ + .handled = LANDLOCK_ACCESS_FS_WRITE_FILE | LANDLOCK_ACCESS_FS_TRUNCATE, + .permitted = LANDLOCK_ACCESS_FS_TRUNCATE, + .expected_open_result = EACCES, +}; + +TEST_F_FORK(ftruncate, open_and_ftruncate) +{ + const char *const path = file1_s1d1; + const struct rule rules[] = { + { + .path = path, + .access = variant->permitted, + }, + {}, + }; + int fd, ruleset_fd; + + /* Enable Landlock. */ + ruleset_fd = create_ruleset(_metadata, variant->handled, rules); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + fd = open(path, O_WRONLY); + EXPECT_EQ(variant->expected_open_result, (fd < 0 ? errno : 0)); + if (fd >= 0) { + EXPECT_EQ(variant->expected_ftruncate_result, + test_ftruncate(fd)); + ASSERT_EQ(0, close(fd)); + } +} + /* clang-format off */ FIXTURE(layout1_bind) {}; /* clang-format on */ -- cgit v1.2.3 From 97b30f9e35709e9d2885efc5c1cd0bf54331ea3d Mon Sep 17 00:00:00 2001 From: Günther Noack Date: Tue, 18 Oct 2022 20:22:12 +0200 Subject: selftests/landlock: Locally define __maybe_unused MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The checkpatch tool started to flag __attribute__(__unused__), which we previously used. The header where this is normally defined is not currently compatible with selftests. This is the same approach as used in selftests/net/psock_lib.h. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20221018182216.301684-8-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/common.h | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'tools/testing') diff --git a/tools/testing/selftests/landlock/common.h b/tools/testing/selftests/landlock/common.h index 7ba18eb23783..7d34592471db 100644 --- a/tools/testing/selftests/landlock/common.h +++ b/tools/testing/selftests/landlock/common.h @@ -17,6 +17,10 @@ #include "../kselftest_harness.h" +#ifndef __maybe_unused +#define __maybe_unused __attribute__((__unused__)) +#endif + /* * TEST_F_FORK() is useful when a test drop privileges but the corresponding * FIXTURE_TEARDOWN() requires them (e.g. to remove files from a directory @@ -140,14 +144,12 @@ static void _init_caps(struct __test_metadata *const _metadata, bool drop_all) } /* We cannot put such helpers in a library because of kselftest_harness.h . */ -__attribute__((__unused__)) static void -disable_caps(struct __test_metadata *const _metadata) +static void __maybe_unused disable_caps(struct __test_metadata *const _metadata) { _init_caps(_metadata, false); } -__attribute__((__unused__)) static void -drop_caps(struct __test_metadata *const _metadata) +static void __maybe_unused drop_caps(struct __test_metadata *const _metadata) { _init_caps(_metadata, true); } @@ -176,14 +178,14 @@ static void _effective_cap(struct __test_metadata *const _metadata, } } -__attribute__((__unused__)) static void -set_cap(struct __test_metadata *const _metadata, const cap_value_t caps) +static void __maybe_unused set_cap(struct __test_metadata *const _metadata, + const cap_value_t caps) { _effective_cap(_metadata, caps, CAP_SET); } -__attribute__((__unused__)) static void -clear_cap(struct __test_metadata *const _metadata, const cap_value_t caps) +static void __maybe_unused clear_cap(struct __test_metadata *const _metadata, + const cap_value_t caps) { _effective_cap(_metadata, caps, CAP_CLEAR); } -- cgit v1.2.3 From a1a202a581817312a02b4d0daa6ca16f701f1e8a Mon Sep 17 00:00:00 2001 From: Günther Noack Date: Tue, 18 Oct 2022 20:22:13 +0200 Subject: selftests/landlock: Test FD passing from restricted to unrestricted processes MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A file descriptor created in a restricted process carries Landlock restrictions with it which will apply even if the same opened file is used from an unrestricted process. This change extracts suitable FD-passing helpers from base_test.c and moves them to common.h. We use the fixture variants from the ftruncate fixture to exercise the same scenarios as in the open_and_ftruncate test, but doing the Landlock restriction and open() in a different process than the ftruncate() call. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20221018182216.301684-9-gnoack3000@gmail.com Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/base_test.c | 36 ++------------- tools/testing/selftests/landlock/common.h | 67 ++++++++++++++++++++++++++++ tools/testing/selftests/landlock/fs_test.c | 62 +++++++++++++++++++++++++ 3 files changed, 132 insertions(+), 33 deletions(-) (limited to 'tools/testing') diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c index 72cdae277b02..792c3f0a59b4 100644 --- a/tools/testing/selftests/landlock/base_test.c +++ b/tools/testing/selftests/landlock/base_test.c @@ -263,23 +263,6 @@ TEST(ruleset_fd_transfer) .allowed_access = LANDLOCK_ACCESS_FS_READ_DIR, }; int ruleset_fd_tx, dir_fd; - union { - /* Aligned ancillary data buffer. */ - char buf[CMSG_SPACE(sizeof(ruleset_fd_tx))]; - struct cmsghdr _align; - } cmsg_tx = {}; - char data_tx = '.'; - struct iovec io = { - .iov_base = &data_tx, - .iov_len = sizeof(data_tx), - }; - struct msghdr msg = { - .msg_iov = &io, - .msg_iovlen = 1, - .msg_control = &cmsg_tx.buf, - .msg_controllen = sizeof(cmsg_tx.buf), - }; - struct cmsghdr *cmsg; int socket_fds[2]; pid_t child; int status; @@ -298,33 +281,20 @@ TEST(ruleset_fd_transfer) &path_beneath_attr, 0)); ASSERT_EQ(0, close(path_beneath_attr.parent_fd)); - cmsg = CMSG_FIRSTHDR(&msg); - ASSERT_NE(NULL, cmsg); - cmsg->cmsg_len = CMSG_LEN(sizeof(ruleset_fd_tx)); - cmsg->cmsg_level = SOL_SOCKET; - cmsg->cmsg_type = SCM_RIGHTS; - memcpy(CMSG_DATA(cmsg), &ruleset_fd_tx, sizeof(ruleset_fd_tx)); - /* Sends the ruleset FD over a socketpair and then close it. */ ASSERT_EQ(0, socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, socket_fds)); - ASSERT_EQ(sizeof(data_tx), sendmsg(socket_fds[0], &msg, 0)); + ASSERT_EQ(0, send_fd(socket_fds[0], ruleset_fd_tx)); ASSERT_EQ(0, close(socket_fds[0])); ASSERT_EQ(0, close(ruleset_fd_tx)); child = fork(); ASSERT_LE(0, child); if (child == 0) { - int ruleset_fd_rx; + const int ruleset_fd_rx = recv_fd(socket_fds[1]); - *(char *)msg.msg_iov->iov_base = '\0'; - ASSERT_EQ(sizeof(data_tx), - recvmsg(socket_fds[1], &msg, MSG_CMSG_CLOEXEC)); - ASSERT_EQ('.', *(char *)msg.msg_iov->iov_base); + ASSERT_LE(0, ruleset_fd_rx); ASSERT_EQ(0, close(socket_fds[1])); - cmsg = CMSG_FIRSTHDR(&msg); - ASSERT_EQ(cmsg->cmsg_len, CMSG_LEN(sizeof(ruleset_fd_tx))); - memcpy(&ruleset_fd_rx, CMSG_DATA(cmsg), sizeof(ruleset_fd_tx)); /* Enforces the received ruleset on the child. */ ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)); diff --git a/tools/testing/selftests/landlock/common.h b/tools/testing/selftests/landlock/common.h index 7d34592471db..d7987ae8d7fc 100644 --- a/tools/testing/selftests/landlock/common.h +++ b/tools/testing/selftests/landlock/common.h @@ -10,6 +10,7 @@ #include #include #include +#include #include #include #include @@ -189,3 +190,69 @@ static void __maybe_unused clear_cap(struct __test_metadata *const _metadata, { _effective_cap(_metadata, caps, CAP_CLEAR); } + +/* Receives an FD from a UNIX socket. Returns the received FD, or -errno. */ +static int __maybe_unused recv_fd(int usock) +{ + int fd_rx; + union { + /* Aligned ancillary data buffer. */ + char buf[CMSG_SPACE(sizeof(fd_rx))]; + struct cmsghdr _align; + } cmsg_rx = {}; + char data = '\0'; + struct iovec io = { + .iov_base = &data, + .iov_len = sizeof(data), + }; + struct msghdr msg = { + .msg_iov = &io, + .msg_iovlen = 1, + .msg_control = &cmsg_rx.buf, + .msg_controllen = sizeof(cmsg_rx.buf), + }; + struct cmsghdr *cmsg; + int res; + + res = recvmsg(usock, &msg, MSG_CMSG_CLOEXEC); + if (res < 0) + return -errno; + + cmsg = CMSG_FIRSTHDR(&msg); + if (cmsg->cmsg_len != CMSG_LEN(sizeof(fd_rx))) + return -EIO; + + memcpy(&fd_rx, CMSG_DATA(cmsg), sizeof(fd_rx)); + return fd_rx; +} + +/* Sends an FD on a UNIX socket. Returns 0 on success or -errno. */ +static int __maybe_unused send_fd(int usock, int fd_tx) +{ + union { + /* Aligned ancillary data buffer. */ + char buf[CMSG_SPACE(sizeof(fd_tx))]; + struct cmsghdr _align; + } cmsg_tx = {}; + char data_tx = '.'; + struct iovec io = { + .iov_base = &data_tx, + .iov_len = sizeof(data_tx), + }; + struct msghdr msg = { + .msg_iov = &io, + .msg_iovlen = 1, + .msg_control = &cmsg_tx.buf, + .msg_controllen = sizeof(cmsg_tx.buf), + }; + struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg); + + cmsg->cmsg_len = CMSG_LEN(sizeof(fd_tx)); + cmsg->cmsg_level = SOL_SOCKET; + cmsg->cmsg_type = SCM_RIGHTS; + memcpy(CMSG_DATA(cmsg), &fd_tx, sizeof(fd_tx)); + + if (sendmsg(usock, &msg, 0) < 0) + return -errno; + return 0; +} diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index 308f6f36e8c0..f8aae01a2409 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -3541,6 +3541,68 @@ TEST_F_FORK(ftruncate, open_and_ftruncate) } } +TEST_F_FORK(ftruncate, open_and_ftruncate_in_different_processes) +{ + int child, fd, status; + int socket_fds[2]; + + ASSERT_EQ(0, socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0, + socket_fds)); + + child = fork(); + ASSERT_LE(0, child); + if (child == 0) { + /* + * Enables Landlock in the child process, open a file descriptor + * where truncation is forbidden and send it to the + * non-landlocked parent process. + */ + const char *const path = file1_s1d1; + const struct rule rules[] = { + { + .path = path, + .access = variant->permitted, + }, + {}, + }; + int fd, ruleset_fd; + + ruleset_fd = create_ruleset(_metadata, variant->handled, rules); + ASSERT_LE(0, ruleset_fd); + enforce_ruleset(_metadata, ruleset_fd); + ASSERT_EQ(0, close(ruleset_fd)); + + fd = open(path, O_WRONLY); + ASSERT_EQ(variant->expected_open_result, (fd < 0 ? errno : 0)); + + if (fd >= 0) { + ASSERT_EQ(0, send_fd(socket_fds[0], fd)); + ASSERT_EQ(0, close(fd)); + } + + ASSERT_EQ(0, close(socket_fds[0])); + + _exit(_metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE); + return; + } + + if (variant->expected_open_result == 0) { + fd = recv_fd(socket_fds[1]); + ASSERT_LE(0, fd); + + EXPECT_EQ(variant->expected_ftruncate_result, + test_ftruncate(fd)); + ASSERT_EQ(0, close(fd)); + } + + ASSERT_EQ(child, waitpid(child, &status, 0)); + ASSERT_EQ(1, WIFEXITED(status)); + ASSERT_EQ(EXIT_SUCCESS, WEXITSTATUS(status)); + + ASSERT_EQ(0, close(socket_fds[0])); + ASSERT_EQ(0, close(socket_fds[1])); +} + /* clang-format off */ FIXTURE(layout1_bind) {}; /* clang-format on */ -- cgit v1.2.3 From 0d8c658be264eb2106349c50377ef8a81edc0106 Mon Sep 17 00:00:00 2001 From: Günther Noack Date: Tue, 18 Oct 2022 20:22:14 +0200 Subject: selftests/landlock: Test ftruncate on FDs created by memfd_create(2) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit All file descriptors that are truncatable need to have the Landlock access rights set correctly on the file's Landlock security blob. This is also the case for files that are opened by other means than open(2). Test coverage for security/landlock is 94.7% of 838 lines according to gcc/gcov-11. Signed-off-by: Günther Noack Link: https://lore.kernel.org/r/20221018182216.301684-10-gnoack3000@gmail.com [mic: Add test coverage in commit message] Signed-off-by: Mickaël Salaün --- tools/testing/selftests/landlock/fs_test.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'tools/testing') diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c index f8aae01a2409..d5dab986f612 100644 --- a/tools/testing/selftests/landlock/fs_test.c +++ b/tools/testing/selftests/landlock/fs_test.c @@ -3603,6 +3603,22 @@ TEST_F_FORK(ftruncate, open_and_ftruncate_in_different_processes) ASSERT_EQ(0, close(socket_fds[1])); } +TEST(memfd_ftruncate) +{ + int fd; + + fd = memfd_create("name", MFD_CLOEXEC); + ASSERT_LE(0, fd); + + /* + * Checks that ftruncate is permitted on file descriptors that are + * created in ways other than open(2). + */ + EXPECT_EQ(0, test_ftruncate(fd)); + + ASSERT_EQ(0, close(fd)); +} + /* clang-format off */ FIXTURE(layout1_bind) {}; /* clang-format on */ -- cgit v1.2.3