Re: [PATCH v9 05/12] landlock: Move and rename umask_layers() and init_layer_masks()

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

2/10/2023 8:37 PM, Mickaël Salaün пишет:
> 
> On 16/01/2023 09:58, Konstantin Meskhidze wrote:
>> This patch renames and moves unmask_layers() and init_layer_masks()
>> helpers to ruleset.c to share them with Landlock network implementation
>> in following commits.
>> 
>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
>> ---
>> 
>> Changes since v8:
>> * Refactors commit message.
>> * Adds "landlock_" prefix for moved helpers.
>> 
>> Changes since v7:
>> * Refactors commit message.
>> 
>> Changes since v6:
>> * Moves get_handled_accesses() helper from ruleset.c back to fs.c,
>>    cause it's not used in coming network commits.
>> 
>> Changes since v5:
>> * Splits commit.
>> * Moves init_layer_masks() and get_handled_accesses() helpers
>> to ruleset.c and makes then non-static.
>> * Formats code with clang-format-14.
>> 
>> ---
> 
> [...]
> 
>> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
>> index 3e1cffda128e..22590cac3d56 100644
>> --- a/security/landlock/ruleset.c
>> +++ b/security/landlock/ruleset.c
>> @@ -572,3 +572,101 @@ landlock_find_rule(const struct landlock_ruleset *const ruleset,
>>   	}
>>   	return NULL;
>>   }
>> +
>> +/*
>> + * @layer_masks is read and may be updated according to the access request and
>> + * the matching rule.
>> + *
>> + * 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])
>> +{
>> +	size_t layer_level;
>> +
>> +	if (!access_request || !layer_masks)
>> +		return true;
>> +	if (!rule)
>> +		return false;
>> +
>> +	/*
>> +	 * An access is granted if, for each policy layer, at least one rule
>> +	 * encountered on the pathwalk grants the requested access,
>> +	 * regardless of its position in the layer stack.  We must then check
>> +	 * the remaining layers for each inode, from the first added layer to
>> +	 * the last one.  When there is multiple requested accesses, for each
>> +	 * policy layer, the full set of requested accesses may not be granted
>> +	 * by only one rule, but by the union (binary OR) of multiple rules.
>> +	 * E.g. /a/b <execute> + /a <read> => /a/b <execute + read>
>> +	 */
>> +	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);
>> +		const unsigned long access_req = access_request;
>> +		unsigned long access_bit;
>> +		bool is_empty;
>> +
>> +		/*
>> +		 * Records in @layer_masks which layer grants access to each
>> +		 * requested access.
>> +		 */
>> +		is_empty = true;
>> +		for_each_set_bit(access_bit, &access_req,
>> +				 ARRAY_SIZE(*layer_masks)) {
>> +			if (layer->access & BIT_ULL(access_bit))
>> +				(*layer_masks)[access_bit] &= ~layer_bit;
>> +			is_empty = is_empty && !(*layer_masks)[access_bit];
>> +		}
>> +		if (is_empty)
>> +			return true;
>> +	}
>> +	return false;
>> +}
>> +
>> +/*
> 
> Please keep the original "/**"

   Got it. Thanks.
> 
> 
>> + * init_layer_masks - Initialize layer masks from an access request
>> + *
>> + * Populates @layer_masks such that for each access right in @access_request,
>> + * the bits for all the layers are set where this access right is handled.
>> + *
>> + * @domain: The domain that defines the current restrictions.
>> + * @access_request: The requested access rights to check.
>> + * @layer_masks: The layer masks to populate.
>> + *
>> + * Returns: An access mask where each access right bit is set which is handled
>> + * in any of the active layers in @domain.
>> + */
> .