[PATCH v5 04/15] landlock: helper functions refactoring
Konstantin Meskhidze
konstantin.meskhidze at huawei.com
Mon May 16 15:20:27 UTC 2022
Unmask_layers(), init_layer_masks() and
get_handled_accesses() helper functions move to
ruleset.c and rule_type argument is added.
This modification supports implementing new rule
types into next landlock versions.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
---
Changes since v3:
* Splits commit.
* Refactoring landlock_unmask_layers functions.
Changes since v4:
* Refactoring init_layer_masks(), get_handled_accesses()
and unmask_layers() functions to support multiple rule types.
* Refactoring landlock_get_fs_access_mask() function with
LANDLOCK_MASK_ACCESS_FS mask.
---
security/landlock/fs.c | 158 ++++++++----------------------------
security/landlock/ruleset.c | 152 +++++++++++++++++++++++++++++++---
security/landlock/ruleset.h | 17 +++-
3 files changed, 192 insertions(+), 135 deletions(-)
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 5de24d4dd74c..3506e182b23e 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -211,60 +211,6 @@ find_rule(const struct landlock_ruleset *const domain,
return rule;
}
-/*
- * @layer_masks is read and may be updated according to the access request and
- * the matching rule.
- *
- * Returns true if the request is allowed (i.e. relevant layer masks for the
- * request are empty).
- */
-static inline 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])
-{
- size_t layer_level;
-
- if (!access_request || !layer_masks)
- return true;
- if (!rule)
- return false;
-
- /*
- * An access is granted if, for each policy layer, at least one rule
- * encountered on the pathwalk grants the requested access,
- * regardless of its position in the layer stack. We must then check
- * the remaining layers for each inode, from the first added layer to
- * the last one. When there is multiple requested accesses, for each
- * policy layer, the full set of requested accesses may not be granted
- * by only one rule, but by the union (binary OR) of multiple rules.
- * E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
- */
- for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
- const struct landlock_layer *const layer =
- &rule->layers[layer_level];
- const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
- const unsigned long access_req = access_request;
- unsigned long access_bit;
- bool is_empty;
-
- /*
- * Records in @layer_masks which layer grants access to each
- * requested access.
- */
- is_empty = true;
- for_each_set_bit(access_bit, &access_req,
- ARRAY_SIZE(*layer_masks)) {
- if (layer->access & BIT_ULL(access_bit))
- (*layer_masks)[access_bit] &= ~layer_bit;
- is_empty = is_empty && !(*layer_masks)[access_bit];
- }
- if (is_empty)
- return true;
- }
- return false;
-}
-
/*
* Allows access to pseudo filesystems that will never be mountable (e.g.
* sockfs, pipefs), but can still be reachable through
@@ -277,59 +223,6 @@ static inline bool is_nouser_or_private(const struct dentry *dentry)
unlikely(IS_PRIVATE(d_backing_inode(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;
-
- for (layer_level = 0; layer_level < domain->num_layers;
- layer_level++) {
- if (landlock_get_fs_access_mask(domain, layer_level) &
- BIT_ULL(access_bit)) {
- access_dom |= BIT_ULL(access_bit);
- break;
- }
- }
- }
- return access_dom;
-}
-
-static inline 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 handled_accesses = 0;
- size_t layer_level;
-
- memset(layer_masks, 0, sizeof(*layer_masks));
- /* An empty access request can happen because of O_WRONLY | O_RDWR. */
- if (!access_request)
- return 0;
-
- /* Saves all handled accesses per layer. */
- for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
- const unsigned long access_req = access_request;
- unsigned long access_bit;
-
- for_each_set_bit(access_bit, &access_req,
- ARRAY_SIZE(*layer_masks)) {
- if (landlock_get_fs_access_mask(domain, layer_level) &
- BIT_ULL(access_bit)) {
- (*layer_masks)[access_bit] |=
- BIT_ULL(layer_level);
- handled_accesses |= BIT_ULL(access_bit);
- }
- }
- }
- return handled_accesses;
-}
-
/*
* Check that a destination file hierarchy has more restrictions than a source
* file hierarchy. This is only used for link and rename actions.
@@ -506,7 +399,8 @@ static int check_access_path_dual(
* a superset of the meaningful requested accesses).
*/
access_masked_parent1 = access_masked_parent2 =
- get_handled_accesses(domain);
+ get_handled_accesses(domain, LANDLOCK_RULE_PATH_BENEATH,
+ LANDLOCK_NUM_ACCESS_FS);
is_dom_check = true;
} else {
if (WARN_ON_ONCE(dentry_child1 || dentry_child2))
@@ -519,17 +413,25 @@ static int check_access_path_dual(
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);
+ init_layer_masks(domain,
+ LANDLOCK_MASK_ACCESS_FS,
+ &_layer_masks_child1,
+ sizeof(_layer_masks_child1),
+ LANDLOCK_RULE_PATH_BENEATH),
+ &_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);
+ init_layer_masks(domain,
+ LANDLOCK_MASK_ACCESS_FS,
+ &_layer_masks_child2,
+ sizeof(_layer_masks_child2),
+ LANDLOCK_RULE_PATH_BENEATH),
+ &_layer_masks_child2,
+ ARRAY_SIZE(_layer_masks_child2));
layer_masks_child2 = &_layer_masks_child2;
child2_is_directory = d_is_dir(dentry_child2);
}
@@ -582,14 +484,15 @@ static int check_access_path_dual(
rule = find_rule(domain, walker_path.dentry);
allowed_parent1 = unmask_layers(rule, access_masked_parent1,
- layer_masks_parent1);
+ layer_masks_parent1,
+ ARRAY_SIZE(*layer_masks_parent1));
allowed_parent2 = unmask_layers(rule, access_masked_parent2,
- layer_masks_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)) {
@@ -645,7 +548,9 @@ 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, sizeof(layer_masks),
+ LANDLOCK_RULE_PATH_BENEATH);
return check_access_path_dual(domain, path, access_request,
&layer_masks, NULL, 0, NULL, NULL);
}
@@ -729,7 +634,8 @@ static bool collect_domain_accesses(
return true;
access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
- layer_masks_dom);
+ layer_masks_dom, sizeof(*layer_masks_dom),
+ LANDLOCK_RULE_PATH_BENEATH);
dget(dir);
while (true) {
@@ -737,7 +643,8 @@ 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.
@@ -851,9 +758,10 @@ static int current_check_refer_path(struct dentry *const old_dentry,
* The LANDLOCK_ACCESS_FS_REFER access right is not required
* for same-directory referer (i.e. no reparenting).
*/
- access_request_parent1 = init_layer_masks(
- dom, access_request_parent1 | access_request_parent2,
- &layer_masks_parent1);
+ access_request_parent1 = init_layer_masks(dom,
+ access_request_parent1 | access_request_parent2,
+ &layer_masks_parent1, sizeof(layer_masks_parent1),
+ LANDLOCK_RULE_PATH_BENEATH);
return check_access_path_dual(dom, new_dir,
access_request_parent1,
&layer_masks_parent1, NULL, 0,
@@ -861,7 +769,9 @@ static int current_check_refer_path(struct dentry *const old_dentry,
}
/* Backward compatibility: no reparenting support. */
- if (!(get_handled_accesses(dom) & LANDLOCK_ACCESS_FS_REFER))
+ if (!(get_handled_accesses(dom, LANDLOCK_RULE_PATH_BENEATH,
+ LANDLOCK_NUM_ACCESS_FS) &
+ LANDLOCK_ACCESS_FS_REFER))
return -EXDEV;
access_request_parent1 |= LANDLOCK_ACCESS_FS_REFER;
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 4b4c9953bb32..c4ed783d655b 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -233,7 +233,8 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
&(*layers)[0]);
if (IS_ERR(new_rule))
return PTR_ERR(new_rule);
- rb_replace_node(&this->node, &new_rule->node, &ruleset->root_inode);
+ rb_replace_node(&this->node, &new_rule->node,
+ &ruleset->root_inode);
free_rule(this, rule_type);
break;
}
@@ -246,7 +247,8 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
return -E2BIG;
switch (rule_type) {
case LANDLOCK_RULE_PATH_BENEATH:
- new_rule = create_rule(object_ptr, 0, layers, num_layers, NULL);
+ new_rule = create_rule(object_ptr, 0, layers,
+ num_layers, NULL);
if (IS_ERR(new_rule))
return PTR_ERR(new_rule);
rb_link_node(&new_rule->node, parent_node, walker_node);
@@ -281,8 +283,8 @@ int landlock_insert_rule(struct landlock_ruleset *const ruleset,
} };
build_check_layer();
- return insert_rule(ruleset, object_ptr, object_data, rule_type, &layers,
- ARRAY_SIZE(layers));
+ return insert_rule(ruleset, object_ptr, object_data, rule_type,
+ &layers, ARRAY_SIZE(layers));
}
static inline void get_hierarchy(struct landlock_hierarchy *const hierarchy)
@@ -335,8 +337,9 @@ static int tree_merge(struct landlock_ruleset *const src,
switch (rule_type) {
case LANDLOCK_RULE_PATH_BENEATH:
- err = insert_rule(dst, walker_rule->object.ptr, 0, rule_type,
- &layers, ARRAY_SIZE(layers));
+ err = insert_rule(dst, walker_rule->object.ptr, 0,
+ rule_type, &layers,
+ ARRAY_SIZE(layers));
break;
}
if (err)
@@ -433,9 +436,13 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
err = -EINVAL;
goto out_unlock;
}
- /* Copies the parent layer stack and leaves a space for the new layer. */
+ /*
+ * Copies the parent layer stack and leaves a space
+ * for the new layer.
+ */
memcpy(child->access_masks, parent->access_masks,
- flex_array_size(parent, access_masks, parent->num_layers));
+ flex_array_size(parent, access_masks,
+ parent->num_layers));
if (WARN_ON_ONCE(!parent->hierarchy)) {
err = -EINVAL;
@@ -455,8 +462,9 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
struct landlock_rule *freeme, *next;
might_sleep();
- rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
- node)
+ rbtree_postorder_for_each_entry_safe(freeme, next,
+ &ruleset->root_inode,
+ node)
free_rule(freeme, LANDLOCK_RULE_PATH_BENEATH);
put_hierarchy(ruleset->hierarchy);
kfree(ruleset);
@@ -577,3 +585,127 @@ const struct landlock_rule *landlock_find_rule(
}
return NULL;
}
+
+access_mask_t get_handled_accesses(
+ const struct landlock_ruleset *const domain,
+ u16 rule_type, u16 num_access)
+{
+ access_mask_t access_dom = 0;
+ unsigned long access_bit;
+
+ switch (rule_type) {
+ case LANDLOCK_RULE_PATH_BENEATH:
+ for (access_bit = 0; access_bit < LANDLOCK_NUM_ACCESS_FS;
+ access_bit++) {
+ size_t layer_level;
+
+ for (layer_level = 0; layer_level < domain->num_layers;
+ layer_level++) {
+ if (landlock_get_fs_access_mask(domain,
+ layer_level) &
+ BIT_ULL(access_bit)) {
+ access_dom |= BIT_ULL(access_bit);
+ break;
+ }
+ }
+ }
+ break;
+ default:
+ break;
+ }
+ return access_dom;
+}
+
+/*
+ * @layer_masks is read and may be updated according to the access request and
+ * the matching rule.
+ *
+ * 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)[], size_t masks_array_size)
+{
+ size_t layer_level;
+
+ if (!access_request || !layer_masks)
+ return true;
+ if (!rule)
+ return false;
+
+ /*
+ * An access is granted if, for each policy layer, at least one rule
+ * encountered on the pathwalk grants the requested access,
+ * regardless of its position in the layer stack. We must then check
+ * the remaining layers for each inode, from the first added layer to
+ * the last one. When there is multiple requested accesses, for each
+ * policy layer, the full set of requested accesses may not be granted
+ * by only one rule, but by the union (binary OR) of multiple rules.
+ * E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
+ */
+ for (layer_level = 0; layer_level < rule->num_layers; layer_level++) {
+ const struct landlock_layer *const layer =
+ &rule->layers[layer_level];
+ const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);
+ const unsigned long access_req = access_request;
+ unsigned long access_bit;
+ bool is_empty;
+
+ /*
+ * Records in @layer_masks which layer grants access to each
+ * requested access.
+ */
+ is_empty = true;
+ 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];
+ }
+ if (is_empty)
+ return true;
+ }
+ return false;
+}
+
+access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
+ const access_mask_t access_request,
+ layer_mask_t (*const layer_masks)[],
+ size_t masks_size,
+ u16 rule_type)
+{
+ access_mask_t handled_accesses = 0;
+ size_t layer_level;
+
+ memset(layer_masks, 0, masks_size);
+
+ /* An empty access request can happen because of O_WRONLY | O_RDWR. */
+ if (!access_request)
+ return 0;
+
+ /* Saves all handled accesses per layer. */
+ for (layer_level = 0; layer_level < domain->num_layers;
+ layer_level++) {
+ const unsigned long access_req = access_request;
+ unsigned long access_bit;
+
+ switch (rule_type) {
+ case LANDLOCK_RULE_PATH_BENEATH:
+ for_each_set_bit(access_bit, &access_req,
+ LANDLOCK_NUM_ACCESS_FS) {
+ if (landlock_get_fs_access_mask(domain,
+ layer_level) &
+ BIT_ULL(access_bit)) {
+ (*layer_masks)[access_bit] |=
+ BIT_ULL(layer_level);
+ handled_accesses |=
+ BIT_ULL(access_bit);
+ }
+ }
+ break;
+ default:
+ return 0;
+ }
+ }
+ return handled_accesses;
+}
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 3066e5d7180c..f3cd890d0348 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -195,7 +195,22 @@ static inline u32 landlock_get_fs_access_mask(
const struct landlock_ruleset *ruleset,
u16 mask_level)
{
- return ruleset->access_masks[mask_level];
+ return (ruleset->access_masks[mask_level] & LANDLOCK_MASK_ACCESS_FS);
}
+access_mask_t get_handled_accesses(
+ const struct landlock_ruleset *const domain,
+ u16 rule_type, u16 num_access);
+
+bool unmask_layers(const struct landlock_rule *const rule,
+ const access_mask_t access_request,
+ layer_mask_t (*const layer_masks)[],
+ 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)[],
+ size_t masks_size,
+ u16 rule_type);
+
#endif /* _SECURITY_LANDLOCK_RULESET_H */
--
2.25.1
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