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Message-ID: <20241014124835.1152246-2-mic@digikod.net>
Date: Mon, 14 Oct 2024 14:48:33 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Günther Noack <gnoack@...gle.com>,
Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>
Cc: Mickaël Salaün <mic@...ikod.net>,
Konstantin Meskhidze <konstantin.meskhidze@...wei.com>,
Paul Moore <paul@...l-moore.com>,
Tahera Fahimi <fahimitahera@...il.com>,
linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org
Subject: [PATCH v2 1/3] landlock: Refactor filesystem access mask management
Replace get_raw_handled_fs_accesses() with a generic
landlock_merge_access_masks(), and replace the get_fs_domain()
implementation with a call to the new landlock_match_ruleset() helper.
These helpers will also be useful for other types of access.
Replace struct access_masks with union access_masks that includes a new
"all" field to simplify mask filtering.
Cc: Günther Noack <gnoack@...gle.com>
Cc: Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>
Signed-off-by: Mickaël Salaün <mic@...ikod.net>
Link: https://lore.kernel.org/r/20241014124835.1152246-2-mic@digikod.net
---
Changes since v1:
* Rename landlock_filter_access_masks() to landlock_match_ruleset().
* Rename local variables from domain to ruleset to mach helpers'
semantic. We'll rename and move these helpers when we'll have a
dedicated domain struct type.
* Rename the all_fs mask to any_fs.
* Add documentation, as suggested by Günther.
---
security/landlock/fs.c | 21 +++---------
security/landlock/ruleset.h | 66 +++++++++++++++++++++++++++++-------
security/landlock/syscalls.c | 2 +-
3 files changed, 59 insertions(+), 30 deletions(-)
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 7d79fc8abe21..5ab770442702 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -388,33 +388,22 @@ static bool is_nouser_or_private(const struct dentry *dentry)
unlikely(IS_PRIVATE(d_backing_inode(dentry))));
}
-static access_mask_t
-get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain)
-{
- access_mask_t access_dom = 0;
- size_t layer_level;
-
- for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
- access_dom |=
- landlock_get_raw_fs_access_mask(domain, layer_level);
- return access_dom;
-}
-
static access_mask_t
get_handled_fs_accesses(const struct landlock_ruleset *const domain)
{
/* Handles all initially denied by default access rights. */
- return get_raw_handled_fs_accesses(domain) |
+ return landlock_merge_access_masks(domain).fs |
LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
}
static const struct landlock_ruleset *
get_fs_domain(const struct landlock_ruleset *const domain)
{
- if (!domain || !get_raw_handled_fs_accesses(domain))
- return NULL;
+ const union access_masks any_fs = {
+ .fs = ~0,
+ };
- return domain;
+ return landlock_match_ruleset(domain, any_fs);
}
static const struct landlock_ruleset *get_current_fs_domain(void)
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 61bdbc550172..c62a9c92ed64 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -41,12 +41,19 @@ static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_SCOPE);
static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
/* Ruleset access masks. */
-struct access_masks {
- access_mask_t fs : LANDLOCK_NUM_ACCESS_FS;
- access_mask_t net : LANDLOCK_NUM_ACCESS_NET;
- access_mask_t scope : LANDLOCK_NUM_SCOPE;
+union access_masks {
+ struct {
+ access_mask_t fs : LANDLOCK_NUM_ACCESS_FS;
+ access_mask_t net : LANDLOCK_NUM_ACCESS_NET;
+ access_mask_t scope : LANDLOCK_NUM_SCOPE;
+ };
+ u32 all;
};
+/* Makes sure all fields are covered. */
+static_assert(sizeof(((union access_masks *)NULL)->all) ==
+ sizeof(union access_masks));
+
typedef u16 layer_mask_t;
/* Makes sure all layers can be checked. */
static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
@@ -229,7 +236,7 @@ struct landlock_ruleset {
* layers are set once and never changed for the
* lifetime of the ruleset.
*/
- struct access_masks access_masks[];
+ union access_masks access_masks[];
};
};
};
@@ -260,6 +267,46 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
refcount_inc(&ruleset->usage);
}
+/**
+ * landlock_merge_access_masks - Return the merge of a ruleset's access_masks
+ *
+ * @ruleset: Landlock ruleset (used as a domain)
+ *
+ * Returns: an access_masks result of the OR of all the ruleset's access masks.
+ */
+static inline union access_masks
+landlock_merge_access_masks(const struct landlock_ruleset *const ruleset)
+{
+ size_t layer_level;
+ union access_masks matches = {};
+
+ for (layer_level = 0; layer_level < ruleset->num_layers; layer_level++)
+ matches.all |= ruleset->access_masks[layer_level].all;
+
+ return matches;
+}
+
+/**
+ * landlock_match_ruleset - Return @ruleset if any @masks right matches
+ *
+ * @ruleset: Landlock ruleset (used as a domain)
+ * @masks: access masks
+ *
+ * Returns: @ruleset if @masks matches, or NULL otherwise.
+ */
+static inline const struct landlock_ruleset *
+landlock_match_ruleset(const struct landlock_ruleset *const ruleset,
+ const union access_masks masks)
+{
+ if (!ruleset)
+ return NULL;
+
+ if (landlock_merge_access_masks(ruleset).all & masks.all)
+ return ruleset;
+
+ return NULL;
+}
+
static inline void
landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
const access_mask_t fs_access_mask,
@@ -295,19 +342,12 @@ landlock_add_scope_mask(struct landlock_ruleset *const ruleset,
ruleset->access_masks[layer_level].scope |= mask;
}
-static inline access_mask_t
-landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset,
- const u16 layer_level)
-{
- return ruleset->access_masks[layer_level].fs;
-}
-
static inline access_mask_t
landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
const u16 layer_level)
{
/* Handles all initially denied by default access rights. */
- return landlock_get_raw_fs_access_mask(ruleset, layer_level) |
+ return ruleset->access_masks[layer_level].fs |
LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
}
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index f5a0e7182ec0..c097d356fa45 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -329,7 +329,7 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
return -ENOMSG;
/* Checks that allowed_access matches the @ruleset constraints. */
- mask = landlock_get_raw_fs_access_mask(ruleset, 0);
+ mask = ruleset->access_masks[0].fs;
if ((path_beneath_attr.allowed_access | mask) != mask)
return -EINVAL;
--
2.47.0
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