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landlock: Refactor layer helpers

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Add a new key_type argument to the landlock_init_layer_masks() helper.
Add a masks_array_size argument to the landlock_unmask_layers() helper.
These modifications support implementing new rule types in the next
Landlock versions.

Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-7-konstantin.meskhidze@huawei.com
Signed-off-by: Mickaël Salaün <mic@digikod.net>
This commit is contained in:
Konstantin Meskhidze 2023-10-26 09:47:45 +08:00 committed by Mickaël Salaün
parent 0e74101129
commit 7a11275c37
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GPG Key ID: E5E3D0E88C82F6D2
3 changed files with 66 additions and 42 deletions
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43
security/landlock/fs.c
View File

@ -442,20 +442,22 @@ static bool is_access_to_paths_allowed(
}
if (unlikely(dentry_child1)) {
landlock_unmask_layers(find_rule(domain, dentry_child1),
landlock_init_layer_masks(
domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child1),
&_layer_masks_child1);
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 = &_layer_masks_child1;
child1_is_directory = d_is_dir(dentry_child1);
}
if (unlikely(dentry_child2)) {
landlock_unmask_layers(find_rule(domain, dentry_child2),
landlock_init_layer_masks(
domain, LANDLOCK_MASK_ACCESS_FS,
&_layer_masks_child2),
&_layer_masks_child2);
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 = &_layer_masks_child2;
child2_is_directory = d_is_dir(dentry_child2);
}
@ -508,14 +510,15 @@ static bool is_access_to_paths_allowed(
rule = find_rule(domain, walker_path.dentry);
allowed_parent1 = landlock_unmask_layers(
rule, access_masked_parent1, layer_masks_parent1);
rule, access_masked_parent1, layer_masks_parent1,
ARRAY_SIZE(*layer_masks_parent1));
allowed_parent2 = landlock_unmask_layers(
rule, access_masked_parent2, layer_masks_parent2);
rule, access_masked_parent2, layer_masks_parent2,
ARRAY_SIZE(*layer_masks_parent2));
/* Stops when a rule from each layer grants access. */
if (allowed_parent1 && allowed_parent2)
break;
jump_up:
if (walker_path.dentry == walker_path.mnt->mnt_root) {
if (follow_up(&walker_path)) {
@ -554,8 +557,8 @@ static inline int check_access_path(const struct landlock_ruleset *const domain,
{
layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_FS] = {};
access_request =
landlock_init_layer_masks(domain, access_request, &layer_masks);
access_request = landlock_init_layer_masks(
domain, access_request, &layer_masks, LANDLOCK_KEY_INODE);
if (is_access_to_paths_allowed(domain, path, access_request,
&layer_masks, NULL, 0, NULL, NULL))
return 0;
@ -641,7 +644,8 @@ static bool collect_domain_accesses(
return true;
access_dom = landlock_init_layer_masks(domain, LANDLOCK_MASK_ACCESS_FS,
layer_masks_dom);
layer_masks_dom,
LANDLOCK_KEY_INODE);
dget(dir);
while (true) {
@ -649,7 +653,8 @@ static bool collect_domain_accesses(
/* Gets all layers allowing all domain accesses. */
if (landlock_unmask_layers(find_rule(domain, dir), access_dom,
layer_masks_dom)) {
layer_masks_dom,
ARRAY_SIZE(*layer_masks_dom))) {
/*
* Stops when all handled accesses are allowed by at
* least one rule in each layer.
@ -764,7 +769,7 @@ static int current_check_refer_path(struct dentry *const old_dentry,
*/
access_request_parent1 = landlock_init_layer_masks(
dom, access_request_parent1 | access_request_parent2,
&layer_masks_parent1);
&layer_masks_parent1, LANDLOCK_KEY_INODE);
if (is_access_to_paths_allowed(
dom, new_dir, access_request_parent1,
&layer_masks_parent1, NULL, 0, NULL, NULL))
@ -1140,7 +1145,7 @@ static int hook_file_open(struct file *const file)
if (is_access_to_paths_allowed(
dom, &file->f_path,
landlock_init_layer_masks(dom, full_access_request,
&layer_masks),
&layer_masks, LANDLOCK_KEY_INODE),
&layer_masks, NULL, 0, NULL, NULL)) {
allowed_access = full_access_request;
} else {

48
security/landlock/ruleset.c
View File

@ -573,14 +573,15 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
/*
* @layer_masks is read and may be updated according to the access request and
* the matching rule.
* @masks_array_size must be equal to ARRAY_SIZE(*layer_masks).
*
* 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])
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)
{
size_t layer_level;
@ -612,8 +613,7 @@ bool landlock_unmask_layers(
* requested access.
*/
is_empty = true;
for_each_set_bit(access_bit, &access_req,
ARRAY_SIZE(*layer_masks)) {
for_each_set_bit(access_bit, &access_req, masks_array_size) {
if (layer->access & BIT_ULL(access_bit))
(*layer_masks)[access_bit] &= ~layer_bit;
is_empty = is_empty && !(*layer_masks)[access_bit];
@ -624,6 +624,10 @@ bool landlock_unmask_layers(
return false;
}
typedef access_mask_t
get_access_mask_t(const struct landlock_ruleset *const ruleset,
const u16 layer_level);
/**
* landlock_init_layer_masks - Initialize layer masks from an access request
*
@ -633,19 +637,34 @@ bool landlock_unmask_layers(
* @domain: The domain that defines the current restrictions.
* @access_request: The requested access rights to check.
* @layer_masks: The layer masks to populate.
* @key_type: The key type to switch between access masks of different types.
*
* 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
landlock_init_layer_masks(const struct landlock_ruleset *const domain,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[],
const enum landlock_key_type key_type)
{
access_mask_t handled_accesses = 0;
size_t layer_level;
size_t layer_level, num_access;
get_access_mask_t *get_access_mask;
switch (key_type) {
case LANDLOCK_KEY_INODE:
get_access_mask = landlock_get_fs_access_mask;
num_access = LANDLOCK_NUM_ACCESS_FS;
break;
default:
WARN_ON_ONCE(1);
return 0;
}
memset(layer_masks, 0,
array_size(sizeof((*layer_masks)[0]), num_access));
memset(layer_masks, 0, sizeof(*layer_masks));
/* An empty access request can happen because of O_WRONLY | O_RDWR. */
if (!access_request)
return 0;
@ -655,10 +674,9 @@ access_mask_t landlock_init_layer_masks(
const unsigned long access_req = access_request;
unsigned long access_bit;
for_each_set_bit(access_bit, &access_req,
ARRAY_SIZE(*layer_masks)) {
for_each_set_bit(access_bit, &access_req, num_access) {
if (BIT_ULL(access_bit) &
landlock_get_fs_access_mask(domain, layer_level)) {
get_access_mask(domain, layer_level)) {
(*layer_masks)[access_bit] |=
BIT_ULL(layer_level);
handled_accesses |= BIT_ULL(access_bit);

17
security/landlock/ruleset.h
View File

@ -267,14 +267,15 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
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]);
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);
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
landlock_init_layer_masks(const struct landlock_ruleset *const domain,
const access_mask_t access_request,
layer_mask_t (*const layer_masks)[],
const enum landlock_key_type key_type);
#endif /* _SECURITY_LANDLOCK_RULESET_H */