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Date:   Mon, 28 Nov 2022 05:53:52 +0300
From:   "Konstantin Meskhidze (A)" <konstantin.meskhidze@...wei.com>
To:     Mickaël Salaün <mic@...ikod.net>
CC:     <willemdebruijn.kernel@...il.com>, <gnoack3000@...il.com>,
        <linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
        <netfilter-devel@...r.kernel.org>, <artem.kuzin@...wei.com>
Subject: Re: [PATCH v8 01/12] landlock: Make ruleset's access masks more
 generic



11/17/2022 9:41 PM, Mickaël Salaün пишет:
> 
> On 21/10/2022 17:26, Konstantin Meskhidze wrote:
>> To support network type rules, this modification renames ruleset's
>> access masks and modifies it's type to access_masks_t. This patch
>> adds filesystem helper functions to add and get filesystem mask.
>> 
>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
>> ---
>> 
>> Changes since v7:
>> * Refactors commit message.
>> 
>> Changes since v6:
>> * Adds a new access_masks_t for struct ruleset.
>> * Renames landlock_set_fs_access_mask() to landlock_add_fs_access_mask()
>>    because it OR values.
>> * Makes landlock_add_fs_access_mask() more resilient incorrect values.
>> * Refactors landlock_get_fs_access_mask().
>> 
>> Changes since v6:
>> * Adds a new access_masks_t for struct ruleset.
>> * Renames landlock_set_fs_access_mask() to landlock_add_fs_access_mask()
>>    because it OR values.
>> * Makes landlock_add_fs_access_mask() more resilient incorrect values.
>> * Refactors landlock_get_fs_access_mask().
>> 
>> Changes since v5:
>> * Changes access_mask_t to u32.
>> * Formats code with clang-format-14.
>> 
>> Changes since v4:
>> * Deletes struct landlock_access_mask.
>> 
>> Changes since v3:
>> * Splits commit.
>> * Adds get_mask, set_mask helpers for filesystem.
>> * Adds new struct landlock_access_mask.
>> 
>> ---
>>   security/landlock/fs.c       | 10 +++++-----
>>   security/landlock/limits.h   |  1 +
>>   security/landlock/ruleset.c  | 17 +++++++++--------
>>   security/landlock/ruleset.h  | 35 +++++++++++++++++++++++++++++++----
>>   security/landlock/syscalls.c |  7 ++++---
>>   5 files changed, 50 insertions(+), 20 deletions(-)
>> 
>> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
>> index adcea0fe7e68..0d57c6479d29 100644
>> --- a/security/landlock/fs.c
>> +++ b/security/landlock/fs.c
>> @@ -178,9 +178,9 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
>>   		return -EINVAL;
>> 
>>   	/* Transforms relative access rights to absolute ones. */
>> -	access_rights |=
>> -		LANDLOCK_MASK_ACCESS_FS &
>> -		~(ruleset->fs_access_masks[0] | ACCESS_INITIALLY_DENIED);
>> +	access_rights |= LANDLOCK_MASK_ACCESS_FS &
>> +			 ~(landlock_get_fs_access_mask(ruleset, 0) |
>> +			   ACCESS_INITIALLY_DENIED);
>>   	object = get_inode_object(d_backing_inode(path->dentry));
>>   	if (IS_ERR(object))
>>   		return PTR_ERR(object);
>> @@ -294,7 +294,7 @@ get_handled_accesses(const struct landlock_ruleset *const domain)
>>   	size_t layer_level;
>> 
>>   	for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
>> -		access_dom |= domain->fs_access_masks[layer_level];
>> +		access_dom |= landlock_get_fs_access_mask(domain, layer_level);
>>   	return access_dom & LANDLOCK_MASK_ACCESS_FS;
> 
> You can remove `& LANDLOCK_MASK_ACCESS_FS` here because it is now part
> of landlock_get_fs_access_mask().

   Ok. I got it. Thanks.
> 
> 
>>   }
>> 
>> @@ -336,7 +336,7 @@ init_layer_masks(const struct landlock_ruleset *const domain,
>>   			 * access rights.
>>   			 */
>>   			if (BIT_ULL(access_bit) &
>> -			    (domain->fs_access_masks[layer_level] |
>> +			    (landlock_get_fs_access_mask(domain, layer_level) |
>>   			     ACCESS_INITIALLY_DENIED)) {
>>   				(*layer_masks)[access_bit] |=
>>   					BIT_ULL(layer_level);
>> diff --git a/security/landlock/limits.h b/security/landlock/limits.h
>> index 82288f0e9e5e..bafb3b8dc677 100644
>> --- a/security/landlock/limits.h
>> +++ b/security/landlock/limits.h
>> @@ -21,6 +21,7 @@
>>   #define LANDLOCK_LAST_ACCESS_FS		LANDLOCK_ACCESS_FS_TRUNCATE
>>   #define LANDLOCK_MASK_ACCESS_FS		((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
>>   #define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
>> +#define LANDLOCK_SHIFT_ACCESS_FS	0
>> 
>>   /* clang-format on */
>> 
>> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
>> index 996484f98bfd..1f3188b4e313 100644
>> --- a/security/landlock/ruleset.c
>> +++ b/security/landlock/ruleset.c
>> @@ -29,7 +29,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
>>   	struct landlock_ruleset *new_ruleset;
>> 
>>   	new_ruleset =
>> -		kzalloc(struct_size(new_ruleset, fs_access_masks, num_layers),
>> +		kzalloc(struct_size(new_ruleset, access_masks, num_layers),
>>   			GFP_KERNEL_ACCOUNT);
>>   	if (!new_ruleset)
>>   		return ERR_PTR(-ENOMEM);
>> @@ -40,7 +40,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
>>   	/*
>>   	 * hierarchy = NULL
>>   	 * num_rules = 0
>> -	 * fs_access_masks[] = 0
>> +	 * access_masks[] = 0
>>   	 */
>>   	return new_ruleset;
>>   }
>> @@ -55,7 +55,7 @@ landlock_create_ruleset(const access_mask_t fs_access_mask)
>>   		return ERR_PTR(-ENOMSG);
>>   	new_ruleset = create_ruleset(1);
>>   	if (!IS_ERR(new_ruleset))
>> -		new_ruleset->fs_access_masks[0] = fs_access_mask;
>> +		landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0);
>>   	return new_ruleset;
>>   }
>> 
>> @@ -117,11 +117,12 @@ static void build_check_ruleset(void)
>>   		.num_rules = ~0,
>>   		.num_layers = ~0,
>>   	};
>> -	typeof(ruleset.fs_access_masks[0]) fs_access_mask = ~0;
>> +	typeof(ruleset.access_masks[0]) access_masks = ~0;
>> 
>>   	BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
>>   	BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
>> -	BUILD_BUG_ON(fs_access_mask < LANDLOCK_MASK_ACCESS_FS);
>> +	BUILD_BUG_ON(access_masks <
>> +		     (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS));
>>   }
>> 
>>   /**
>> @@ -281,7 +282,7 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>>   		err = -EINVAL;
>>   		goto out_unlock;
>>   	}
>> -	dst->fs_access_masks[dst->num_layers - 1] = src->fs_access_masks[0];
>> +	dst->access_masks[dst->num_layers - 1] = src->access_masks[0];
>> 
>>   	/* Merges the @src tree. */
>>   	rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, &src->root,
>> @@ -340,8 +341,8 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
>>   		goto out_unlock;
>>   	}
>>   	/* Copies the parent layer stack and leaves a space for the new layer. */
>> -	memcpy(child->fs_access_masks, parent->fs_access_masks,
>> -	       flex_array_size(parent, fs_access_masks, parent->num_layers));
>> +	memcpy(child->access_masks, parent->access_masks,
>> +	       flex_array_size(parent, access_masks, parent->num_layers));
>> 
>>   	if (WARN_ON_ONCE(!parent->hierarchy)) {
>>   		err = -EINVAL;
>> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
>> index d43231b783e4..f2ad932d396c 100644
>> --- a/security/landlock/ruleset.h
>> +++ b/security/landlock/ruleset.h
>> @@ -25,6 +25,11 @@ static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
>>   /* Makes sure for_each_set_bit() and for_each_clear_bit() calls are OK. */
>>   static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
>> 
>> +/* Ruleset access masks. */
>> +typedef u16 access_masks_t;
>> +/* Makes sure all ruleset access rights can be stored. */
>> +static_assert(BITS_PER_TYPE(access_masks_t) >= LANDLOCK_NUM_ACCESS_FS);
>> +
>>   typedef u16 layer_mask_t;
>>   /* Makes sure all layers can be checked. */
>>   static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
>> @@ -110,7 +115,7 @@ struct landlock_ruleset {
>>   		 * section.  This is only used by
>>   		 * landlock_put_ruleset_deferred() when @usage reaches zero.
>>   		 * The fields @lock, @usage, @num_rules, @num_layers and
>> -		 * @fs_access_masks are then unused.
>> +		 * @access_masks are then unused.
>>   		 */
>>   		struct work_struct work_free;
>>   		struct {
>> @@ -137,7 +142,7 @@ struct landlock_ruleset {
>>   			 */
>>   			u32 num_layers;
>>   			/**
>> -			 * @fs_access_masks: Contains the subset of filesystem
>> +			 * @access_masks: Contains the subset of filesystem
>>   			 * actions that are restricted by a ruleset.  A domain
>>   			 * saves all layers of merged rulesets in a stack
>>   			 * (FAM), starting from the first layer to the last
>> @@ -148,13 +153,13 @@ struct landlock_ruleset {
>>   			 * layers are set once and never changed for the
>>   			 * lifetime of the ruleset.
>>   			 */
>> -			access_mask_t fs_access_masks[];
>> +			access_masks_t access_masks[];
>>   		};
>>   	};
>>   };
>> 
>>   struct landlock_ruleset *
>> -landlock_create_ruleset(const access_mask_t fs_access_mask);
>> +landlock_create_ruleset(const access_mask_t access_mask);
>> 
>>   void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
>>   void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
>> @@ -177,4 +182,26 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
>>   		refcount_inc(&ruleset->usage);
>>   }
>> 
>> +static inline void
>> +landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
>> +			    const access_mask_t fs_access_mask,
>> +			    const u16 layer_level)
>> +{
>> +	access_mask_t fs_mask = fs_access_mask & LANDLOCK_MASK_ACCESS_FS;
>> +
>> +	/* Should already be checked in sys_landlock_create_ruleset(). */
>> +	WARN_ON_ONCE(fs_access_mask != fs_mask);
>> +	// TODO: Add tests to check "|=" and not "="
> 
> This todo should be done and removed. No more todos must remain.
> 
   I delete it in 10/12 Patch when add network seltests.
> 
>> +	ruleset->access_masks[layer_level] |=
>> +		(fs_mask << LANDLOCK_SHIFT_ACCESS_FS);
>> +}
>> +
>> +static inline access_mask_t
>> +landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
>> +			    const u16 layer_level)
>> +{
>> +	return (ruleset->access_masks[layer_level] >>
>> +		LANDLOCK_SHIFT_ACCESS_FS) &
>> +	       LANDLOCK_MASK_ACCESS_FS;
>> +}
>>   #endif /* _SECURITY_LANDLOCK_RULESET_H */
>> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
>> index 245cc650a4dc..71aca7f990bc 100644
>> --- a/security/landlock/syscalls.c
>> +++ b/security/landlock/syscalls.c
>> @@ -346,10 +346,11 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
>>   	}
>>   	/*
>>   	 * Checks that allowed_access matches the @ruleset constraints
>> -	 * (ruleset->fs_access_masks[0] is automatically upgraded to 64-bits).
>> +	 * (ruleset->access_masks[0] is automatically upgraded to 64-bits).
>>   	 */
>> -	if ((path_beneath_attr.allowed_access | ruleset->fs_access_masks[0]) !=
>> -	    ruleset->fs_access_masks[0]) {
>> +	if ((path_beneath_attr.allowed_access |
>> +	     landlock_get_fs_access_mask(ruleset, 0)) !=
>> +	    landlock_get_fs_access_mask(ruleset, 0)) {
>>   		err = -EINVAL;
>>   		goto out_put_ruleset;
>>   	}
>> --
>> 2.25.1
>> 
> 
> I'll send a patch to be applied after this one.
> .

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