[PATCH 5.18 789/879] landlock: Create find_rule() from unmask_layers()

Greg Kroah-Hartman
2022-06-08T00:55:58Z

From: Mickaël Salaün <mic@digikod.net>

commit 2cd7cd6eed88b8383cfddce589afe9c0ae1d19b4 upstream.

This refactoring will be useful in a following commit.

Reviewed-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20220506161102.525323-4-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
security/landlock/fs.c | 41 ++++++++++++++++++++++++++++-------------
1 file changed, 28 insertions(+), 13 deletions(-)

--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -183,23 +183,36 @@ int landlock_append_fs_rule(struct landl

/* Access-control management */

-static inline layer_mask_t
-unmask_layers(const struct landlock_ruleset *const domain,
- const struct path *const path, const access_mask_t access_request,
- layer_mask_t layer_mask)
+/*
+ * The lifetime of the returned rule is tied to @domain.
+ *
+ * Returns NULL if no rule is found or if @dentry is negative.
+ */
+static inline const struct landlock_rule *
+find_rule(const struct landlock_ruleset *const domain,
+ const struct dentry *const dentry)
{
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);
+ /* Ignores nonexistent leafs. */
+ if (d_is_negative(dentry))
+ return NULL;
+
+ inode = d_backing_inode(dentry);
rcu_read_lock();
rule = landlock_find_rule(
domain, rcu_dereference(landlock_inode(inode)->object));
rcu_read_unlock();
+ return rule;
+}
+
+static inline layer_mask_t unmask_layers(const struct landlock_rule *const rule,
+ const access_mask_t access_request,
+ layer_mask_t layer_mask)
+{
+ size_t layer_level;
+
if (!rule)
return layer_mask;

@@ -210,8 +223,9 @@ unmask_layers(const struct landlock_rule
* 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];
+ 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);

/* Checks that the layer grants access to the full request. */
@@ -269,8 +283,9 @@ static int check_access_path(const struc
while (true) {
struct dentry *parent_dentry;

- layer_mask = unmask_layers(domain, &walker_path, access_request,
- layer_mask);
+ layer_mask =
+ unmask_layers(find_rule(domain, walker_path.dentry),
+ access_request, layer_mask);
if (layer_mask == 0) {
/* Stops when a rule from each layer grants access. */
allowed = true;