Landlock fix for v6.0-rc4
-----BEGIN PGP SIGNATURE----- iIYEABYIAC4WIQSVyBthFV4iTW/VU1/l49DojIL20gUCYxILwxAcbWljQGRpZ2lr b2QubmV0AAoJEOXj0OiMgvbSdu4BANqLdLqVhylwJRjZS91rpxrtwp6bOTxtR6+Q aSVtD2ZlAQCEl4/twUSO0mARkkprXXqNsjGcQ8wxN9JrxtcXAlaBCQ== =uVMR -----END PGP SIGNATURE----- Merge tag 'landlock-6.0-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux Pull landlock fix from Mickaël Salaün: "This fixes a mis-handling of the LANDLOCK_ACCESS_FS_REFER right when multiple rulesets/domains are stacked. The expected behaviour was that an additional ruleset can only restrict the set of permitted operations, but in this particular case, it was potentially possible to re-gain the LANDLOCK_ACCESS_FS_REFER right" * tag 'landlock-6.0-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux: landlock: Fix file reparenting without explicit LANDLOCK_ACCESS_FS_REFER
This commit is contained in:
Linus Torvalds
commit
0c95f02269
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@ -149,6 +149,16 @@ retry:
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LANDLOCK_ACCESS_FS_READ_FILE)
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/* clang-format on */
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/*
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* All access rights that are denied by default whether they are handled or not
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* by a ruleset/layer. This must be ORed with all ruleset->fs_access_masks[]
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* entries when we need to get the absolute handled access masks.
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*/
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/* clang-format off */
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#define ACCESS_INITIALLY_DENIED ( \
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LANDLOCK_ACCESS_FS_REFER)
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/* clang-format on */
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/*
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* @path: Should have been checked by get_path_from_fd().
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*/
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@ -167,7 +177,9 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
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return -EINVAL;
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/* Transforms relative access rights to absolute ones. */
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access_rights |= LANDLOCK_MASK_ACCESS_FS & ~ruleset->fs_access_masks[0];
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access_rights |=
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LANDLOCK_MASK_ACCESS_FS &
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~(ruleset->fs_access_masks[0] | ACCESS_INITIALLY_DENIED);
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object = get_inode_object(d_backing_inode(path->dentry));
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if (IS_ERR(object))
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return PTR_ERR(object);
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@ -277,23 +289,12 @@ static inline bool is_nouser_or_private(const struct dentry *dentry)
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static inline access_mask_t
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get_handled_accesses(const struct landlock_ruleset *const domain)
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{
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access_mask_t access_dom = 0;
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unsigned long access_bit;
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access_mask_t access_dom = ACCESS_INITIALLY_DENIED;
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size_t layer_level;
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for (access_bit = 0; access_bit < LANDLOCK_NUM_ACCESS_FS;
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access_bit++) {
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size_t layer_level;
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for (layer_level = 0; layer_level < domain->num_layers;
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layer_level++) {
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if (domain->fs_access_masks[layer_level] &
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BIT_ULL(access_bit)) {
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access_dom |= BIT_ULL(access_bit);
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break;
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}
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}
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}
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return access_dom;
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for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
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access_dom |= domain->fs_access_masks[layer_level];
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return access_dom & LANDLOCK_MASK_ACCESS_FS;
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}
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static inline access_mask_t
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@ -316,8 +317,13 @@ init_layer_masks(const struct landlock_ruleset *const domain,
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for_each_set_bit(access_bit, &access_req,
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ARRAY_SIZE(*layer_masks)) {
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if (domain->fs_access_masks[layer_level] &
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BIT_ULL(access_bit)) {
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/*
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* Artificially handles all initially denied by default
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* access rights.
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*/
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if (BIT_ULL(access_bit) &
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(domain->fs_access_masks[layer_level] |
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ACCESS_INITIALLY_DENIED)) {
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(*layer_masks)[access_bit] |=
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BIT_ULL(layer_level);
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handled_accesses |= BIT_ULL(access_bit);
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@ -857,10 +863,6 @@ static int current_check_refer_path(struct dentry *const old_dentry,
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NULL, NULL);
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}
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/* Backward compatibility: no reparenting support. */
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if (!(get_handled_accesses(dom) & LANDLOCK_ACCESS_FS_REFER))
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return -EXDEV;
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access_request_parent1 |= LANDLOCK_ACCESS_FS_REFER;
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access_request_parent2 |= LANDLOCK_ACCESS_FS_REFER;
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@ -4,7 +4,7 @@
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*
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* Copyright © 2017-2020 Mickaël Salaün <mic@digikod.net>
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* Copyright © 2020 ANSSI
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* Copyright © 2020-2021 Microsoft Corporation
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* Copyright © 2020-2022 Microsoft Corporation
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*/
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#define _GNU_SOURCE
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@ -371,6 +371,13 @@ TEST_F_FORK(layout1, inval)
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ASSERT_EQ(EINVAL, errno);
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path_beneath.allowed_access &= ~LANDLOCK_ACCESS_FS_EXECUTE;
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/* Tests with denied-by-default access right. */
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path_beneath.allowed_access |= LANDLOCK_ACCESS_FS_REFER;
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ASSERT_EQ(-1, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
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&path_beneath, 0));
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ASSERT_EQ(EINVAL, errno);
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path_beneath.allowed_access &= ~LANDLOCK_ACCESS_FS_REFER;
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/* Test with unknown (64-bits) value. */
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path_beneath.allowed_access |= (1ULL << 60);
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ASSERT_EQ(-1, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
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@ -1826,6 +1833,20 @@ TEST_F_FORK(layout1, link)
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ASSERT_EQ(0, link(file1_s1d3, file2_s1d3));
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}
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static int test_rename(const char *const oldpath, const char *const newpath)
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{
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if (rename(oldpath, newpath))
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return errno;
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return 0;
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}
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static int test_exchange(const char *const oldpath, const char *const newpath)
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{
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if (renameat2(AT_FDCWD, oldpath, AT_FDCWD, newpath, RENAME_EXCHANGE))
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return errno;
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return 0;
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}
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TEST_F_FORK(layout1, rename_file)
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{
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const struct rule rules[] = {
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@ -1867,10 +1888,10 @@ TEST_F_FORK(layout1, rename_file)
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* to a different directory (which allows file removal).
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*/
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ASSERT_EQ(-1, rename(file1_s2d1, file1_s1d3));
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ASSERT_EQ(EXDEV, errno);
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ASSERT_EQ(EACCES, errno);
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ASSERT_EQ(-1, renameat2(AT_FDCWD, file1_s2d1, AT_FDCWD, file1_s1d3,
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RENAME_EXCHANGE));
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ASSERT_EQ(EXDEV, errno);
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ASSERT_EQ(EACCES, errno);
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ASSERT_EQ(-1, renameat2(AT_FDCWD, dir_s2d2, AT_FDCWD, file1_s1d3,
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RENAME_EXCHANGE));
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ASSERT_EQ(EXDEV, errno);
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@ -1894,7 +1915,7 @@ TEST_F_FORK(layout1, rename_file)
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ASSERT_EQ(EXDEV, errno);
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ASSERT_EQ(0, unlink(file1_s1d3));
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ASSERT_EQ(-1, rename(file1_s2d1, file1_s1d3));
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ASSERT_EQ(EXDEV, errno);
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ASSERT_EQ(EACCES, errno);
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/* Exchanges and renames files with same parent. */
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ASSERT_EQ(0, renameat2(AT_FDCWD, file2_s2d3, AT_FDCWD, file1_s2d3,
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@ -2014,6 +2035,115 @@ TEST_F_FORK(layout1, reparent_refer)
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ASSERT_EQ(0, rename(dir_s1d3, dir_s2d3));
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}
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/* Checks renames beneath dir_s1d1. */
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static void refer_denied_by_default(struct __test_metadata *const _metadata,
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const struct rule layer1[],
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const int layer1_err,
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const struct rule layer2[])
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{
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int ruleset_fd;
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ASSERT_EQ(0, unlink(file1_s1d2));
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ruleset_fd = create_ruleset(_metadata, layer1[0].access, layer1);
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ASSERT_LE(0, ruleset_fd);
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enforce_ruleset(_metadata, ruleset_fd);
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ASSERT_EQ(0, close(ruleset_fd));
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/*
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* If the first layer handles LANDLOCK_ACCESS_FS_REFER (according to
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* layer1_err), then it allows some different-parent renames and links.
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*/
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ASSERT_EQ(layer1_err, test_rename(file1_s1d1, file1_s1d2));
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if (layer1_err == 0)
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ASSERT_EQ(layer1_err, test_rename(file1_s1d2, file1_s1d1));
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ASSERT_EQ(layer1_err, test_exchange(file2_s1d1, file2_s1d2));
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ASSERT_EQ(layer1_err, test_exchange(file2_s1d2, file2_s1d1));
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ruleset_fd = create_ruleset(_metadata, layer2[0].access, layer2);
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ASSERT_LE(0, ruleset_fd);
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enforce_ruleset(_metadata, ruleset_fd);
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ASSERT_EQ(0, close(ruleset_fd));
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/*
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* Now, either the first or the second layer does not handle
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* LANDLOCK_ACCESS_FS_REFER, which means that any different-parent
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* renames and links are denied, thus making the layer handling
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* LANDLOCK_ACCESS_FS_REFER null and void.
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*/
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ASSERT_EQ(EXDEV, test_rename(file1_s1d1, file1_s1d2));
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ASSERT_EQ(EXDEV, test_exchange(file2_s1d1, file2_s1d2));
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ASSERT_EQ(EXDEV, test_exchange(file2_s1d2, file2_s1d1));
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}
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const struct rule layer_dir_s1d1_refer[] = {
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{
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.path = dir_s1d1,
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.access = LANDLOCK_ACCESS_FS_REFER,
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},
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{},
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};
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const struct rule layer_dir_s1d1_execute[] = {
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{
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/* Matches a parent directory. */
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.path = dir_s1d1,
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.access = LANDLOCK_ACCESS_FS_EXECUTE,
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},
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{},
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};
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const struct rule layer_dir_s2d1_execute[] = {
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{
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/* Does not match a parent directory. */
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.path = dir_s2d1,
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.access = LANDLOCK_ACCESS_FS_EXECUTE,
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},
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{},
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};
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/*
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* Tests precedence over renames: denied by default for different parent
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* directories, *with* a rule matching a parent directory, but not directly
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* denying access (with MAKE_REG nor REMOVE).
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*/
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TEST_F_FORK(layout1, refer_denied_by_default1)
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{
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refer_denied_by_default(_metadata, layer_dir_s1d1_refer, 0,
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layer_dir_s1d1_execute);
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}
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/*
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* Same test but this time turning around the ABI version order: the first
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* layer does not handle LANDLOCK_ACCESS_FS_REFER.
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*/
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TEST_F_FORK(layout1, refer_denied_by_default2)
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{
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refer_denied_by_default(_metadata, layer_dir_s1d1_execute, EXDEV,
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layer_dir_s1d1_refer);
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}
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/*
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* Tests precedence over renames: denied by default for different parent
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* directories, *without* a rule matching a parent directory, but not directly
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* denying access (with MAKE_REG nor REMOVE).
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*/
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TEST_F_FORK(layout1, refer_denied_by_default3)
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{
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refer_denied_by_default(_metadata, layer_dir_s1d1_refer, 0,
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layer_dir_s2d1_execute);
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}
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/*
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* Same test but this time turning around the ABI version order: the first
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* layer does not handle LANDLOCK_ACCESS_FS_REFER.
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*/
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TEST_F_FORK(layout1, refer_denied_by_default4)
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{
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refer_denied_by_default(_metadata, layer_dir_s2d1_execute, EXDEV,
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layer_dir_s1d1_refer);
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}
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TEST_F_FORK(layout1, reparent_link)
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{
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const struct rule layer1[] = {
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@ -2336,11 +2466,12 @@ TEST_F_FORK(layout1, reparent_exdev_layers_rename1)
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ASSERT_EQ(EXDEV, errno);
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/*
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* However, moving the file2_s1d3 file below dir_s2d3 is allowed
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* because it cannot inherit MAKE_REG nor MAKE_DIR rights (which are
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* dedicated to directories).
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* Moving the file2_s1d3 file below dir_s2d3 is denied because the
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* second layer does not handle REFER, which is always denied by
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* default.
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*/
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ASSERT_EQ(0, rename(file2_s1d3, file1_s2d3));
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ASSERT_EQ(-1, rename(file2_s1d3, file1_s2d3));
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ASSERT_EQ(EXDEV, errno);
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}
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TEST_F_FORK(layout1, reparent_exdev_layers_rename2)
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@ -2373,8 +2504,12 @@ TEST_F_FORK(layout1, reparent_exdev_layers_rename2)
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ASSERT_EQ(EACCES, errno);
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ASSERT_EQ(-1, rename(file1_s1d1, file1_s2d3));
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ASSERT_EQ(EXDEV, errno);
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/* Modify layout! */
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ASSERT_EQ(0, rename(file2_s1d2, file1_s2d3));
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/*
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* Modifying the layout is now denied because the second layer does not
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* handle REFER, which is always denied by default.
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*/
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ASSERT_EQ(-1, rename(file2_s1d2, file1_s2d3));
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ASSERT_EQ(EXDEV, errno);
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/* Without REFER source, EACCES wins over EXDEV. */
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ASSERT_EQ(-1, rename(dir_s1d1, file1_s2d2));
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