Re: [PATCH v9 06/12] landlock: Refactor _unmask_layers() and _init_layer_masks()

["Konstantin Meskhidze (A)" <konstantin.meskhidze@huawei.com>]

2/21/2023 9:07 PM, Mickaël Salaün пишет:
> It's not "_unmask_layers() and _init_layer_masks()": there is no "_"
> prefixes.
> Using "landlock_unmask_layers()" in the subject would be too long, so
> you can replace it with "landlock: Refactor layer helpers".
> For consistency, you can change the previous patch's subject to
> "landlock: Move and rename layer helpers"
> 
> Anyway, please send a new patch series. Most of the kernel code should
> be good and I could then push it to -next for testing while reviewing
> the last parts.

   Hi, Mickaël. I was on a short vacation. Sorry for late reply.
   I will reply your review and send a new patch ASAP.

   Regards,
   Konstantin

> 
> 
> On 16/01/2023 09:58, Konstantin Meskhidze wrote:
>> Add 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: Mickaël Salaün <mic@digikod.net>
>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
>> ---
>> 
>> Changes since v8:
>> * None.
>> 
>> Changes since v7:
>> * Refactors commit message, adds a co-developer.
>> * Minor fixes.
>> 
>> Changes since v6:
>> * Removes masks_size attribute from init_layer_masks().
>> * Refactors init_layer_masks() with new landlock_key_type.
>> 
>> Changes since v5:
>> * Splits commit.
>> * Formats code with clang-format-14.
>> 
>> Changes since v4:
>> * Refactors init_layer_masks(), get_handled_accesses()
>> and unmask_layers() functions to support multiple rule types.
>> * Refactors landlock_get_fs_access_mask() function with
>> LANDLOCK_MASK_ACCESS_FS mask.
>> 
>> Changes since v3:
>> * Splits commit.
>> * Refactors landlock_unmask_layers functions.
>> 
>> ---
>>   security/landlock/fs.c      | 43 ++++++++++++++++--------------
>>   security/landlock/ruleset.c | 52 ++++++++++++++++++++++++++-----------
>>   security/landlock/ruleset.h | 17 ++++++------
>>   3 files changed, 70 insertions(+), 42 deletions(-)
>> 
>> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
>> index 73a7399f93ba..a73dbd3f9ddb 100644
>> --- a/security/landlock/fs.c
>> +++ b/security/landlock/fs.c
>> @@ -441,20 +441,22 @@ 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);
>>   	}
>> @@ -507,14 +509,15 @@ 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)) {
>> @@ -553,8 +556,8 @@ static 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;
>> @@ -640,7 +643,8 @@ 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) {
>> @@ -648,7 +652,8 @@ 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.
>> @@ -763,7 +768,7 @@ 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))
>> @@ -1139,7 +1144,7 @@ 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 {
>> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
>> index 22590cac3d56..9748b54b42fe 100644
>> --- a/security/landlock/ruleset.c
>> +++ b/security/landlock/ruleset.c
>> @@ -576,14 +576,15 @@ 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;
>>   
>> @@ -615,8 +616,7 @@ 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];
>> @@ -627,6 +627,10 @@ bool landlock_unmask_layers(
>>   	return false;
>>   }
>>   
>> +typedef access_mask_t
>> +get_access_mask_t(const struct landlock_ruleset *const ruleset,
>> +		  const u16 layer_level);
>> +
>>   /*
>>    * init_layer_masks - Initialize layer masks from an access request
>>    *
>> @@ -636,19 +640,34 @@ 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;
>> @@ -658,10 +677,13 @@ 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) {
>> +			/*
>> +			 * Artificially handles all initially denied by default
>> +			 * access rights.
>> +			 */
>>   			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);
>> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
>> index 60a3c4d4d961..77349764e111 100644
>> --- a/security/landlock/ruleset.h
>> +++ b/security/landlock/ruleset.h
>> @@ -266,14 +266,15 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
>>   	return landlock_get_raw_fs_access_mask(ruleset, layer_level) |
>>   	       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 */
> .