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Message-ID: <20230323085226.1432550-7-konstantin.meskhidze@huawei.com>
Date: Thu, 23 Mar 2023 16:52:19 +0800
From: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
To: <mic@...ikod.net>
CC: <willemdebruijn.kernel@...il.com>, <gnoack3000@...il.com>,
<linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
<netfilter-devel@...r.kernel.org>, <yusongping@...wei.com>,
<artem.kuzin@...wei.com>
Subject: [PATCH v10 06/13] landlock: Move and rename layer helpers
This patch renames and moves landlock_unmask_layers() and
landlock_init_layer_masks() helpers to ruleset.c to share
them with Landlock network implementation in following commits.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
---
Changes since v9:
* Minor fixes.
Changes since v8:
* Refactors commit message.
* Adds "landlock_" prefix for moved helpers.
Changes since v7:
* Refactors commit message.
Changes since v6:
* Moves get_handled_accesses() helper from ruleset.c back to fs.c,
cause it's not used in coming network commits.
Changes since v5:
* Splits commit.
* Moves init_layer_masks() and get_handled_accesses() helpers
to ruleset.c and makes then non-static.
* Formats code with clang-format-14.
---
security/landlock/fs.c | 136 ++++++------------------------------
security/landlock/ruleset.c | 98 ++++++++++++++++++++++++++
security/landlock/ruleset.h | 9 +++
3 files changed, 128 insertions(+), 115 deletions(-)
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 6f9c463b291e..10ba5000ce9a 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -215,60 +215,6 @@ 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 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
@@ -293,50 +239,6 @@ get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain)
return access_dom;
}
-/**
- * init_layer_masks - Initialize layer masks from an access request
- *
- * Populates @layer_masks such that for each access right in @access_request,
- * the bits for all the layers are set where this access right is handled.
- *
- * @domain: The domain that defines the current restrictions.
- * @access_request: The requested access rights to check.
- * @layer_masks: The layer masks to populate.
- *
- * Returns: An access mask where each access right bit is set which is handled
- * in any of the active layers in @domain.
- */
-static 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 (BIT_ULL(access_bit) &
- landlock_get_fs_access_mask(domain, layer_level)) {
- (*layer_masks)[access_bit] |=
- BIT_ULL(layer_level);
- handled_accesses |= BIT_ULL(access_bit);
- }
- }
- }
- return handled_accesses;
-}
-
static access_mask_t
get_handled_fs_accesses(const struct landlock_ruleset *const domain)
{
@@ -540,18 +442,20 @@ 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,
+ landlock_unmask_layers(find_rule(domain, dentry_child1),
+ landlock_init_layer_masks(
+ domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child1),
- &_layer_masks_child1);
+ &_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,
+ landlock_unmask_layers(find_rule(domain, dentry_child2),
+ landlock_init_layer_masks(
+ domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child2),
- &_layer_masks_child2);
+ &_layer_masks_child2);
layer_masks_child2 = &_layer_masks_child2;
child2_is_directory = d_is_dir(dentry_child2);
}
@@ -603,10 +507,10 @@ 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 = landlock_unmask_layers(
+ rule, access_masked_parent1, layer_masks_parent1);
+ allowed_parent2 = landlock_unmask_layers(
+ rule, access_masked_parent2, layer_masks_parent2);
/* Stops when a rule from each layer grants access. */
if (allowed_parent1 && allowed_parent2)
@@ -650,7 +554,8 @@ static 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 =
+ landlock_init_layer_masks(domain, access_request, &layer_masks);
if (is_access_to_paths_allowed(domain, path, access_request,
&layer_masks, NULL, 0, NULL, NULL))
return 0;
@@ -735,16 +640,16 @@ static bool collect_domain_accesses(
if (is_nouser_or_private(dir))
return true;
- access_dom = init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
- layer_masks_dom);
+ access_dom = landlock_init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
+ layer_masks_dom);
dget(dir);
while (true) {
struct dentry *parent_dentry;
/* Gets all layers allowing all domain accesses. */
- if (unmask_layers(find_rule(domain, dir), access_dom,
- layer_masks_dom)) {
+ if (landlock_unmask_layers(find_rule(domain, dir), access_dom,
+ layer_masks_dom)) {
/*
* Stops when all handled accesses are allowed by at
* least one rule in each layer.
@@ -857,7 +762,7 @@ 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(
+ access_request_parent1 = landlock_init_layer_masks(
dom, access_request_parent1 | access_request_parent2,
&layer_masks_parent1);
if (is_access_to_paths_allowed(
@@ -1234,7 +1139,8 @@ 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),
+ landlock_init_layer_masks(dom, full_access_request,
+ &layer_masks),
&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 2579c9bbedbc..969ff8c4baff 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -574,3 +574,101 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
}
return NULL;
}
+
+/*
+ * @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 landlock_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;
+}
+
+/**
+ * landlock_init_layer_masks - Initialize layer masks from an access request
+ *
+ * Populates @layer_masks such that for each access right in @access_request,
+ * the bits for all the layers are set where this access right is handled.
+ *
+ * @domain: The domain that defines the current restrictions.
+ * @access_request: The requested access rights to check.
+ * @layer_masks: The layer masks to populate.
+ *
+ * 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 landlock_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 (BIT_ULL(access_bit) &
+ landlock_get_fs_access_mask(domain, layer_level)) {
+ (*layer_masks)[access_bit] |=
+ BIT_ULL(layer_level);
+ handled_accesses |= BIT_ULL(access_bit);
+ }
+ }
+ }
+ return handled_accesses;
+}
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 5e1b1b25def0..3635e709b20d 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -266,5 +266,14 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
return landlock_get_raw_fs_access_mask(ruleset, layer_level) |
LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
}
+bool landlock_unmask_layers(
+ const struct landlock_rule *const rule,
+ const access_mask_t access_request,
+ layer_mask_t (*const layer_masks)[LANDLOCK_NUM_ACCESS_FS]);
+
+access_mask_t landlock_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]);
#endif /* _SECURITY_LANDLOCK_RULESET_H */
--
2.25.1
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