[PATCH v8 05/12] landlock: Refactor unmask_layers() and init_layer_masks()
Konstantin Meskhidze
konstantin.meskhidze at huawei.com
Fri Oct 21 15:26:37 UTC 2022
Adds new key_type argument to init_layer_masks() helper.
Adds masks_array_size argument to unmask_layers() helper.
These modifications support implementing new rule types in the next
Landlock versions.
Co-developed-by: Mickaël Salaün <mic at digikod.net>
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
---
Changes since v7:
* Refactors commit message, adds a co-developer.
* Minor fixes.
Changes since v6:
* Removes masks_size attribute from init_layer_masks().
* Refactors init_layer_masks() with new landlock_key_type.
Changes since v5:
* Splits commit.
* Formats code with clang-format-14.
Changes since v4:
* Refactors init_layer_masks(), get_handled_accesses()
and unmask_layers() functions to support multiple rule types.
* Refactors landlock_get_fs_access_mask() function with
LANDLOCK_MASK_ACCESS_FS mask.
Changes since v3:
* Splits commit.
* Refactors landlock_unmask_layers functions.
---
security/landlock/fs.c | 36 ++++++++++++++++++-------------
security/landlock/ruleset.c | 42 ++++++++++++++++++++++++++-----------
security/landlock/ruleset.h | 11 +++++-----
3 files changed, 58 insertions(+), 31 deletions(-)
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 240e42a8f788..fe76a11483f8 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -435,16 +435,20 @@ static bool is_access_to_paths_allowed(
if (unlikely(dentry_child1)) {
unmask_layers(find_rule(domain, dentry_child1),
init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
- &_layer_masks_child1),
- &_layer_masks_child1);
+ &_layer_masks_child1,
+ LANDLOCK_KEY_INODE),
+ &_layer_masks_child1,
+ ARRAY_SIZE(_layer_masks_child1));
layer_masks_child1 = &_layer_masks_child1;
child1_is_directory = d_is_dir(dentry_child1);
}
if (unlikely(dentry_child2)) {
unmask_layers(find_rule(domain, dentry_child2),
init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
- &_layer_masks_child2),
- &_layer_masks_child2);
+ &_layer_masks_child2,
+ LANDLOCK_KEY_INODE),
+ &_layer_masks_child2,
+ ARRAY_SIZE(_layer_masks_child2));
layer_masks_child2 = &_layer_masks_child2;
child2_is_directory = d_is_dir(dentry_child2);
}
@@ -496,15 +500,16 @@ static bool is_access_to_paths_allowed(
}
rule = find_rule(domain, walker_path.dentry);
- allowed_parent1 = unmask_layers(rule, access_masked_parent1,
- layer_masks_parent1);
- allowed_parent2 = unmask_layers(rule, access_masked_parent2,
- layer_masks_parent2);
+ allowed_parent1 = unmask_layers(
+ rule, access_masked_parent1, layer_masks_parent1,
+ ARRAY_SIZE(*layer_masks_parent1));
+ allowed_parent2 = unmask_layers(
+ rule, access_masked_parent2, layer_masks_parent2,
+ ARRAY_SIZE(*layer_masks_parent2));
/* Stops when a rule from each layer grants access. */
if (allowed_parent1 && allowed_parent2)
break;
-
jump_up:
if (walker_path.dentry == walker_path.mnt->mnt_root) {
if (follow_up(&walker_path)) {
@@ -543,7 +548,8 @@ static inline int check_access_path(const struct landlock_ruleset *const domain,
{
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
- access_request = init_layer_masks(domain, access_request, &layer_masks);
+ access_request = init_layer_masks(domain, access_request, &layer_masks,
+ LANDLOCK_KEY_INODE);
if (is_access_to_paths_allowed(domain, path, access_request,
&layer_masks, NULL, 0, NULL, NULL))
return 0;
@@ -630,7 +636,7 @@ static bool collect_domain_accesses(
return true;
access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
- layer_masks_dom);
+ layer_masks_dom, LANDLOCK_KEY_INODE);
dget(dir);
while (true) {
@@ -638,7 +644,8 @@ static bool collect_domain_accesses(
/* Gets all layers allowing all domain accesses. */
if (unmask_layers(find_rule(domain, dir), access_dom,
- layer_masks_dom)) {
+ layer_masks_dom,
+ ARRAY_SIZE(*layer_masks_dom))) {
/*
* Stops when all handled accesses are allowed by at
* least one rule in each layer.
@@ -754,7 +761,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
*/
access_request_parent1 = init_layer_masks(
dom, access_request_parent1 | access_request_parent2,
- &layer_masks_parent1);
+ &layer_masks_parent1, LANDLOCK_KEY_INODE);
if (is_access_to_paths_allowed(
dom, new_dir, access_request_parent1,
&layer_masks_parent1, NULL, 0, NULL, NULL))
@@ -1131,7 +1138,8 @@ static int hook_file_open(struct file *const file)
if (is_access_to_paths_allowed(
dom, &file->f_path,
- init_layer_masks(dom, full_access_request, &layer_masks),
+ init_layer_masks(dom, full_access_request, &layer_masks,
+ LANDLOCK_KEY_INODE),
&layer_masks, NULL, 0, NULL, NULL)) {
allowed_access = full_access_request;
} else {
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 02ab14439c43..c7cf54ba4f6d 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -576,13 +576,15 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
/*
* @layer_masks is read and may be updated according to the access request and
* the matching rule.
+ * @masks_array_size must be equal to ARRAY_SIZE(*layer_masks).
*
* Returns true if the request is allowed (i.e. relevant layer masks for the
* request are empty).
*/
bool unmask_layers(const struct landlock_rule *const rule,
const access_mask_t access_request,
- layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+ layer_mask_t (*const layer_masks)[],
+ const size_t masks_array_size)
{
size_t layer_level;
@@ -614,8 +616,7 @@ bool unmask_layers(const struct landlock_rule *const rule,
* requested access.
*/
is_empty = true;
- for_each_set_bit(access_bit, &access_req,
- ARRAY_SIZE(*layer_masks)) {
+ for_each_set_bit(access_bit, &access_req, masks_array_size) {
if (layer->access & BIT_ULL(access_bit))
(*layer_masks)[access_bit] &= ~layer_bit;
is_empty = is_empty && !(*layer_masks)[access_bit];
@@ -626,6 +627,10 @@ bool unmask_layers(const struct landlock_rule *const rule,
return false;
}
+typedef access_mask_t
+get_access_mask_t(const struct landlock_ruleset *const ruleset,
+ const u16 layer_level);
+
/**
* init_layer_masks - Initialize layer masks from an access request
*
@@ -635,19 +640,33 @@ bool unmask_layers(const struct landlock_rule *const rule,
* @domain: The domain that defines the current restrictions.
* @access_request: The requested access rights to check.
* @layer_masks: The layer masks to populate.
+ * @key_type: The key type to switch between access masks of different types.
*
* Returns: An access mask where each access right bit is set which is handled
* in any of the active layers in @domain.
*/
-access_mask_t
-init_layer_masks(const struct landlock_ruleset *const domain,
- const access_mask_t access_request,
- layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS])
+access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
+ const access_mask_t access_request,
+ layer_mask_t (*const layer_masks)[],
+ const enum landlock_key_type key_type)
{
access_mask_t handled_accesses = 0;
- size_t layer_level;
+ size_t layer_level, num_access;
+ get_access_mask_t *get_access_mask;
+
+ switch (key_type) {
+ case LANDLOCK_KEY_INODE:
+ get_access_mask = landlock_get_fs_access_mask;
+ num_access = LANDLOCK_NUM_ACCESS_FS;
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ return 0;
+ }
+
+ memset(layer_masks, 0,
+ array_size(sizeof((*layer_masks)[0]), num_access));
- memset(layer_masks, 0, sizeof(*layer_masks));
/* An empty access request can happen because of O_WRONLY | O_RDWR. */
if (!access_request)
return 0;
@@ -657,14 +676,13 @@ init_layer_masks(const struct landlock_ruleset *const domain,
const unsigned long access_req = access_request;
unsigned long access_bit;
- for_each_set_bit(access_bit, &access_req,
- ARRAY_SIZE(*layer_masks)) {
+ for_each_set_bit(access_bit, &access_req, num_access) {
/*
* Artificially handles all initially denied by default
* access rights.
*/
if (BIT_ULL(access_bit) &
- (landlock_get_fs_access_mask(domain, layer_level) |
+ (get_access_mask(domain, layer_level) |
ACCESS_INITIALLY_DENIED)) {
(*layer_masks)[access_bit] |=
BIT_ULL(layer_level);
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 50baff4fcbb4..d9eb79ea9a89 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -259,11 +259,12 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
bool unmask_layers(const struct landlock_rule *const rule,
const access_mask_t access_request,
- layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]);
+ layer_mask_t (*const layer_masks)[],
+ const size_t masks_array_size);
-access_mask_t
-init_layer_masks(const struct landlock_ruleset *const domain,
- const access_mask_t access_request,
- layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]);
+access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
+ const access_mask_t access_request,
+ layer_mask_t (*const layer_masks)[],
+ const enum landlock_key_type key_type);
#endif /* _SECURITY_LANDLOCK_RULESET_H */
--
2.25.1
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