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landlock: Create find_rule() from unmask_layers()

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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>
This commit is contained in:
Mickaël Salaün 2022-05-06 18:10:53 +02:00
parent 75c542d6c6
commit 2cd7cd6eed
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GPG Key ID: E5E3D0E88C82F6D2
1 changed files with 28 additions and 13 deletions
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41
security/landlock/fs.c
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@ -183,23 +183,36 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
/* 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_ruleset *const domain,
* 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 struct landlock_ruleset *const domain,
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;