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authorLinus Torvalds <torvalds@linux-foundation.org>2022-09-03 01:24:08 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2022-09-03 01:24:08 +0300
commit0c95f02269a1ef6c3fae4f46bbdd7a4578d44b8f (patch)
tree11f0c001fad170d08cc1b4a21e6a638b27768b7b /security
parentb307e704574bd4187d4f46212e7ea8189b53f9ab (diff)
parent55e55920bbe3ccf516022c51f5527e7d026b8f1d (diff)
downloadlinux-0c95f02269a1ef6c3fae4f46bbdd7a4578d44b8f.tar.xz
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
Diffstat (limited to 'security')
-rw-r--r--security/landlock/fs.c48
1 files changed, 25 insertions, 23 deletions
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index ec5a6247cd3e..a9dbd99d9ee7 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -150,6 +150,16 @@ retry:
/* clang-format on */
/*
+ * All access rights that are denied by default whether they are handled or not
+ * by a ruleset/layer. This must be ORed with all ruleset->fs_access_masks[]
+ * entries when we need to get the absolute handled access masks.
+ */
+/* clang-format off */
+#define ACCESS_INITIALLY_DENIED ( \
+ LANDLOCK_ACCESS_FS_REFER)
+/* clang-format on */
+
+/*
* @path: Should have been checked by get_path_from_fd().
*/
int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
@@ -167,7 +177,9 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
return -EINVAL;
/* Transforms relative access rights to absolute ones. */
- access_rights |= LANDLOCK_MASK_ACCESS_FS & ~ruleset->fs_access_masks[0];
+ access_rights |=
+ LANDLOCK_MASK_ACCESS_FS &
+ ~(ruleset->fs_access_masks[0] | ACCESS_INITIALLY_DENIED);
object = get_inode_object(d_backing_inode(path->dentry));
if (IS_ERR(object))
return PTR_ERR(object);
@@ -277,23 +289,12 @@ static inline bool is_nouser_or_private(const struct dentry *dentry)
static inline access_mask_t
get_handled_accesses(const struct landlock_ruleset *const domain)
{
- access_mask_t access_dom = 0;
- unsigned long access_bit;
-
- for (access_bit = 0; access_bit < LANDLOCK_NUM_ACCESS_FS;
- access_bit++) {
- size_t layer_level;
+ access_mask_t access_dom = ACCESS_INITIALLY_DENIED;
+ size_t layer_level;
- for (layer_level = 0; layer_level < domain->num_layers;
- layer_level++) {
- if (domain->fs_access_masks[layer_level] &
- BIT_ULL(access_bit)) {
- access_dom |= BIT_ULL(access_bit);
- break;
- }
- }
- }
- return access_dom;
+ for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
+ access_dom |= domain->fs_access_masks[layer_level];
+ return access_dom & LANDLOCK_MASK_ACCESS_FS;
}
static inline access_mask_t
@@ -316,8 +317,13 @@ init_layer_masks(const struct landlock_ruleset *const domain,
for_each_set_bit(access_bit, &access_req,
ARRAY_SIZE(*layer_masks)) {
- if (domain->fs_access_masks[layer_level] &
- BIT_ULL(access_bit)) {
+ /*
+ * Artificially handles all initially denied by default
+ * access rights.
+ */
+ if (BIT_ULL(access_bit) &
+ (domain->fs_access_masks[layer_level] |
+ ACCESS_INITIALLY_DENIED)) {
(*layer_masks)[access_bit] |=
BIT_ULL(layer_level);
handled_accesses |= BIT_ULL(access_bit);
@@ -857,10 +863,6 @@ static int current_check_refer_path(struct dentry *const old_dentry,
NULL, NULL);
}
- /* Backward compatibility: no reparenting support. */
- if (!(get_handled_accesses(dom) & LANDLOCK_ACCESS_FS_REFER))
- return -EXDEV;
-
access_request_parent1 |= LANDLOCK_ACCESS_FS_REFER;
access_request_parent2 |= LANDLOCK_ACCESS_FS_REFER;