[RFC PATCH 1/6] landlock: Add a place for flags to layer rules
Tingmao Wang
m at maowtm.org
Tue Sep 9 00:06:35 UTC 2025
To avoid unnecessarily increasing the size of struct landlock_layer, we
make the layer level a u8 and use the space to store the flags struct.
Signed-off-by: Tingmao Wang <m at maowtm.org>
---
security/landlock/fs.c | 75 ++++++++++++++++++++++++-------------
security/landlock/net.c | 3 +-
security/landlock/ruleset.c | 9 ++++-
security/landlock/ruleset.h | 27 ++++++++++++-
4 files changed, 83 insertions(+), 31 deletions(-)
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index c04f8879ad03..e7eaf55093e9 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -756,10 +756,12 @@ static bool is_access_to_paths_allowed(
const struct path *const path,
const access_mask_t access_request_parent1,
layer_mask_t (*const layer_masks_parent1)[LANDLOCK_NUM_ACCESS_FS],
+ struct collected_rule_flags *const rule_flags_parent1,
struct landlock_request *const log_request_parent1,
struct dentry *const dentry_child1,
const access_mask_t access_request_parent2,
layer_mask_t (*const layer_masks_parent2)[LANDLOCK_NUM_ACCESS_FS],
+ struct collected_rule_flags *const rule_flags_parent2,
struct landlock_request *const log_request_parent2,
struct dentry *const dentry_child2)
{
@@ -810,22 +812,30 @@ static bool is_access_to_paths_allowed(
}
if (unlikely(dentry_child1)) {
+ /*
+ * The rule_flags for child1 should have been included in
+ * rule_flags_masks_parent1 already. We do not bother about it
+ * for domain check.
+ */
landlock_unmask_layers(
find_rule(domain, dentry_child1),
landlock_init_layer_masks(
domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child1, LANDLOCK_KEY_INODE),
- &_layer_masks_child1, ARRAY_SIZE(_layer_masks_child1));
+ &_layer_masks_child1, ARRAY_SIZE(_layer_masks_child1),
+ NULL);
layer_masks_child1 = &_layer_masks_child1;
child1_is_directory = d_is_dir(dentry_child1);
}
if (unlikely(dentry_child2)) {
+ /* See above comment for why NULL is passed as rule_flags_masks */
landlock_unmask_layers(
find_rule(domain, dentry_child2),
landlock_init_layer_masks(
domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child2, LANDLOCK_KEY_INODE),
- &_layer_masks_child2, ARRAY_SIZE(_layer_masks_child2));
+ &_layer_masks_child2, ARRAY_SIZE(_layer_masks_child2),
+ NULL);
layer_masks_child2 = &_layer_masks_child2;
child2_is_directory = d_is_dir(dentry_child2);
}
@@ -881,16 +891,18 @@ static bool is_access_to_paths_allowed(
}
rule = find_rule(domain, walker_path.dentry);
- allowed_parent1 = allowed_parent1 ||
- landlock_unmask_layers(
- rule, access_masked_parent1,
- layer_masks_parent1,
- ARRAY_SIZE(*layer_masks_parent1));
- allowed_parent2 = allowed_parent2 ||
- landlock_unmask_layers(
- rule, access_masked_parent2,
- layer_masks_parent2,
- ARRAY_SIZE(*layer_masks_parent2));
+ allowed_parent1 =
+ allowed_parent1 ||
+ landlock_unmask_layers(rule, access_masked_parent1,
+ layer_masks_parent1,
+ ARRAY_SIZE(*layer_masks_parent1),
+ rule_flags_parent1);
+ allowed_parent2 =
+ allowed_parent2 ||
+ landlock_unmask_layers(rule, access_masked_parent2,
+ layer_masks_parent2,
+ ARRAY_SIZE(*layer_masks_parent2),
+ rule_flags_parent2);
/* Stops when a rule from each layer grants access. */
if (allowed_parent1 && allowed_parent2)
@@ -958,6 +970,7 @@ static int current_check_access_path(const struct path *const path,
const struct landlock_cred_security *const subject =
landlock_get_applicable_subject(current_cred(), masks, NULL);
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
+ struct collected_rule_flags rule_flags = {};
struct landlock_request request = {};
if (!subject)
@@ -967,8 +980,8 @@ static int current_check_access_path(const struct path *const path,
access_request, &layer_masks,
LANDLOCK_KEY_INODE);
if (is_access_to_paths_allowed(subject->domain, path, access_request,
- &layer_masks, &request, NULL, 0, NULL,
- NULL, NULL))
+ &layer_masks, &rule_flags, &request,
+ NULL, 0, NULL, NULL, NULL, NULL))
return 0;
landlock_log_denial(subject, &request);
@@ -1032,7 +1045,8 @@ static access_mask_t maybe_remove(const struct dentry *const dentry)
static bool collect_domain_accesses(
const struct landlock_ruleset *const domain,
const struct dentry *const mnt_root, struct dentry *dir,
- layer_mask_t (*const layer_masks_dom)[LANDLOCK_NUM_ACCESS_FS])
+ layer_mask_t (*const layer_masks_dom)[LANDLOCK_NUM_ACCESS_FS],
+ struct collected_rule_flags *const rule_flags)
{
unsigned long access_dom;
bool ret = false;
@@ -1051,9 +1065,9 @@ static bool collect_domain_accesses(
struct dentry *parent_dentry;
/* Gets all layers allowing all domain accesses. */
- if (landlock_unmask_layers(find_rule(domain, dir), access_dom,
- layer_masks_dom,
- ARRAY_SIZE(*layer_masks_dom))) {
+ if (landlock_unmask_layers(
+ find_rule(domain, dir), access_dom, layer_masks_dom,
+ ARRAY_SIZE(*layer_masks_dom), rule_flags)) {
/*
* Stops when all handled accesses are allowed by at
* least one rule in each layer.
@@ -1140,6 +1154,8 @@ static int current_check_refer_path(struct dentry *const old_dentry,
struct dentry *old_parent;
layer_mask_t layer_masks_parent1[LANDLOCK_NUM_ACCESS_FS] = {},
layer_masks_parent2[LANDLOCK_NUM_ACCESS_FS] = {};
+ struct collected_rule_flags rule_flags_parent1 = {},
+ rule_flags_parent2 = {};
struct landlock_request request1 = {}, request2 = {};
if (!subject)
@@ -1172,10 +1188,10 @@ static int current_check_refer_path(struct dentry *const old_dentry,
subject->domain,
access_request_parent1 | access_request_parent2,
&layer_masks_parent1, LANDLOCK_KEY_INODE);
- if (is_access_to_paths_allowed(subject->domain, new_dir,
- access_request_parent1,
- &layer_masks_parent1, &request1,
- NULL, 0, NULL, NULL, NULL))
+ if (is_access_to_paths_allowed(
+ subject->domain, new_dir, access_request_parent1,
+ &layer_masks_parent1, &rule_flags_parent1,
+ &request1, NULL, 0, NULL, NULL, NULL, NULL))
return 0;
landlock_log_denial(subject, &request1);
@@ -1201,10 +1217,12 @@ static int current_check_refer_path(struct dentry *const old_dentry,
/* new_dir->dentry is equal to new_dentry->d_parent */
allow_parent1 = collect_domain_accesses(subject->domain, mnt_dir.dentry,
old_parent,
- &layer_masks_parent1);
+ &layer_masks_parent1,
+ &rule_flags_parent1);
allow_parent2 = collect_domain_accesses(subject->domain, mnt_dir.dentry,
new_dir->dentry,
- &layer_masks_parent2);
+ &layer_masks_parent2,
+ &rule_flags_parent2);
if (allow_parent1 && allow_parent2)
return 0;
@@ -1217,8 +1235,9 @@ static int current_check_refer_path(struct dentry *const old_dentry,
*/
if (is_access_to_paths_allowed(
subject->domain, &mnt_dir, access_request_parent1,
- &layer_masks_parent1, &request1, old_dentry,
- access_request_parent2, &layer_masks_parent2, &request2,
+ &layer_masks_parent1, &rule_flags_parent1, &request1,
+ old_dentry, access_request_parent2, &layer_masks_parent2,
+ &rule_flags_parent2, &request2,
exchange ? new_dentry : NULL))
return 0;
@@ -1616,6 +1635,7 @@ static bool is_device(const struct file *const file)
static int hook_file_open(struct file *const file)
{
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
+ struct collected_rule_flags rule_flags = {};
access_mask_t open_access_request, full_access_request, allowed_access,
optional_access;
const struct landlock_cred_security *const subject =
@@ -1647,7 +1667,8 @@ static int hook_file_open(struct file *const file)
landlock_init_layer_masks(subject->domain,
full_access_request, &layer_masks,
LANDLOCK_KEY_INODE),
- &layer_masks, &request, NULL, 0, NULL, NULL, NULL)) {
+ &layer_masks, &rule_flags, &request, NULL, 0, NULL, NULL,
+ NULL, NULL)) {
allowed_access = full_access_request;
} else {
unsigned long access_bit;
diff --git a/security/landlock/net.c b/security/landlock/net.c
index 1f3915a90a80..fc6369dffa51 100644
--- a/security/landlock/net.c
+++ b/security/landlock/net.c
@@ -48,6 +48,7 @@ static int current_check_access_socket(struct socket *const sock,
{
__be16 port;
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
+ struct collected_rule_flags rule_flags = {};
const struct landlock_rule *rule;
struct landlock_id id = {
.type = LANDLOCK_KEY_NET_PORT,
@@ -179,7 +180,7 @@ static int current_check_access_socket(struct socket *const sock,
access_request, &layer_masks,
LANDLOCK_KEY_NET_PORT);
if (landlock_unmask_layers(rule, access_request, &layer_masks,
- ARRAY_SIZE(layer_masks)))
+ ARRAY_SIZE(layer_masks), &rule_flags))
return 0;
audit_net.family = address->sa_family;
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index ce7940efea51..3aa4e33ac95b 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -616,7 +616,8 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
bool landlock_unmask_layers(const struct landlock_rule *const rule,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[],
- const size_t masks_array_size)
+ const size_t masks_array_size,
+ struct collected_rule_flags *const rule_flags)
{
size_t layer_level;
@@ -643,6 +644,12 @@ bool landlock_unmask_layers(const struct landlock_rule *const rule,
unsigned long access_bit;
bool is_empty;
+ if (rule_flags) {
+ /* Collect rule flags for each layer */
+ if (layer->flags.quiet)
+ rule_flags->quiet_masks |= layer_bit;
+ }
+
/*
* Records in @layer_masks which layer grants access to each
* requested access.
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 5da9a64f5af7..d4b70b6af137 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -29,7 +29,18 @@ struct landlock_layer {
/**
* @level: Position of this layer in the layer stack.
*/
- u16 level;
+ u8 level;
+ /**
+ * @flags: Bitfield for special flags attached to this rule.
+ */
+ struct {
+ /**
+ * @quiet: Suppresses denial audit logs for the object covered by
+ * this rule in this domain. For fs rules, this inherits down the
+ * file hierarchy.
+ */
+ bool quiet:1;
+ } flags;
/**
* @access: Bitfield of allowed actions on the kernel object. They are
* relative to the object type (e.g. %LANDLOCK_ACTION_FS_READ).
@@ -37,6 +48,17 @@ struct landlock_layer {
access_mask_t access;
};
+
+/**
+ * struct collected_rule_flags - Hold accumulated flags for each layer
+ */
+struct collected_rule_flags {
+ /**
+ * @quiet_masks: Layers for which the quiet flag is effective.
+ */
+ layer_mask_t quiet_masks;
+};
+
/**
* union landlock_key - Key of a ruleset's red-black tree
*/
@@ -304,7 +326,8 @@ landlock_get_scope_mask(const struct landlock_ruleset *const ruleset,
bool landlock_unmask_layers(const struct landlock_rule *const rule,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[],
- const size_t masks_array_size);
+ const size_t masks_array_size,
+ struct collected_rule_flags *const rule_flags);
access_mask_t
landlock_init_layer_masks(const struct landlock_ruleset *const domain,
--
2.51.0
More information about the Linux-security-module-archive
mailing list