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Message-ID: <20220309134459.6448-6-konstantin.meskhidze@huawei.com>
Date: Wed, 9 Mar 2022 21:44:49 +0800
From: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
To: <mic@...ikod.net>
CC: <willemdebruijn.kernel@...il.com>,
<linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
<netfilter-devel@...r.kernel.org>, <yusongping@...wei.com>,
<artem.kuzin@...wei.com>, <anton.sirazetdinov@...wei.com>
Subject: [RFC PATCH v4 05/15] landlock: unmask_layers() function refactoring
Unmask_layers() helper function moves 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@...wei.com>
---
Changes since v3:
* Split commit.
* Refactoring landlock_unmask_layers functions.
---
security/landlock/fs.c | 67 +++++++++----------------------------
security/landlock/ruleset.c | 44 ++++++++++++++++++++++++
security/landlock/ruleset.h | 5 +++
3 files changed, 64 insertions(+), 52 deletions(-)
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 1497948d754f..75ebdce5cd16 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -178,51 +178,6 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
return err;
}
-/* Access-control management */
-
-static inline u64 unmask_layers(
- const struct landlock_ruleset *const domain,
- const struct path *const path, const u32 access_request,
- u64 layer_mask)
-{
- const struct landlock_rule *rule;
- const struct inode *inode;
- size_t i;
-
- if (d_is_negative(path->dentry))
- /* Ignore nonexistent leafs. */
- return layer_mask;
- inode = d_backing_inode(path->dentry);
- rcu_read_lock();
- rule = landlock_find_rule(domain,
- (uintptr_t)rcu_dereference(landlock_inode(inode)->object),
- LANDLOCK_RULE_PATH_BENEATH);
- rcu_read_unlock();
- if (!rule)
- return layer_mask;
-
- /*
- * An access is granted if, for each policy layer, at least one rule
- * encountered on the pathwalk grants the requested accesses,
- * regardless of their position in the layer stack. We must then check
- * the remaining layers for each inode, from the first added layer to
- * the last one.
- */
- for (i = 0; i < rule->num_layers; i++) {
- const struct landlock_layer *const layer = &rule->layers[i];
- const u64 layer_level = BIT_ULL(layer->level - 1);
-
- /* Checks that the layer grants access to the full request. */
- if ((layer->access & access_request) == access_request) {
- layer_mask &= ~layer_level;
-
- if (layer_mask == 0)
- return layer_mask;
- }
- }
- return layer_mask;
-}
-
static int check_access_path(const struct landlock_ruleset *const domain,
const struct path *const path, u32 access_request)
{
@@ -268,15 +223,23 @@ static int check_access_path(const struct landlock_ruleset *const domain,
*/
while (true) {
struct dentry *parent_dentry;
+ const struct inode *inode;
+ struct landlock_object *object_ptr;
- layer_mask = unmask_layers(domain, &walker_path,
- access_request, layer_mask);
- if (layer_mask == 0) {
- /* Stops when a rule from each layer grants access. */
- allowed = true;
- break;
+ /* Ignore nonexistent leafs. */
+ if (!d_is_negative(walker_path.dentry)) {
+
+ inode = d_backing_inode(walker_path.dentry);
+ object_ptr = landlock_inode(inode)->object;
+ layer_mask = landlock_unmask_layers(domain, object_ptr,
+ access_request, layer_mask,
+ LANDLOCK_RULE_PATH_BENEATH);
+ if (layer_mask == 0) {
+ /* Stops when a rule from each layer grants access. */
+ allowed = true;
+ break;
+ }
}
-
jump_up:
if (walker_path.dentry == walker_path.mnt->mnt_root) {
if (follow_up(&walker_path)) {
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index f2baa1c96b16..7179b10f3538 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -582,3 +582,47 @@ const struct landlock_rule *landlock_find_rule(
}
return NULL;
}
+
+/* Access-control management */
+u64 landlock_unmask_layers(const struct landlock_ruleset *const domain,
+ const struct landlock_object *object_ptr,
+ const u32 access_request, u64 layer_mask,
+ const u16 rule_type)
+{
+ const struct landlock_rule *rule;
+ size_t i;
+
+ switch (rule_type) {
+ case LANDLOCK_RULE_PATH_BENEATH:
+ rcu_read_lock();
+ rule = landlock_find_rule(domain,
+ (uintptr_t)rcu_dereference(object_ptr),
+ LANDLOCK_RULE_PATH_BENEATH);
+ rcu_read_unlock();
+ break;
+ }
+
+ if (!rule)
+ return layer_mask;
+
+ /*
+ * An access is granted if, for each policy layer, at least one rule
+ * encountered on the pathwalk grants the requested accesses,
+ * regardless of their position in the layer stack. We must then check
+ * the remaining layers for each inode, from the first added layer to
+ * the last one.
+ */
+ for (i = 0; i < rule->num_layers; i++) {
+ const struct landlock_layer *const layer = &rule->layers[i];
+ const u64 layer_level = BIT_ULL(layer->level - 1);
+
+ /* Checks that the layer grants access to the full request. */
+ if ((layer->access & access_request) == access_request) {
+ layer_mask &= ~layer_level;
+
+ if (layer_mask == 0)
+ return layer_mask;
+ }
+ }
+ return layer_mask;
+}
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 088b8d95f653..0a7d4b1f51fd 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -183,4 +183,9 @@ void landlock_set_fs_access_mask(struct landlock_ruleset *ruleset,
u32 landlock_get_fs_access_mask(const struct landlock_ruleset *ruleset, u16 mask_level);
+u64 landlock_unmask_layers(const struct landlock_ruleset *const domain,
+ const struct landlock_object *object_ptr,
+ const u32 access_request, u64 layer_mask,
+ const u16 rule_type);
+
#endif /* _SECURITY_LANDLOCK_RULESET_H */
--
2.25.1
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