Message-ID: <544f0edb-0b5a-17c3-57a1-a373723ef37f@digikod.net>
Date:   Tue, 17 May 2022 10:27:45 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
Cc:     willemdebruijn.kernel@...il.com,
        linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, yusongping@...wei.com,
        anton.sirazetdinov@...wei.com
Subject: Re: [PATCH v5 07/15] landlock: add support network rules



On 16/05/2022 17:20, Konstantin Meskhidze wrote:
> This modification adds network rules support
> in internal landlock functions (presented in ruleset.c)
> and landlock_create_ruleset syscall.
> 
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
> ---
> 
> Changes since v3:
> * Split commit.
> * Add network rule support for internal landlock functions.
> * Add set_mask and get_mask for network.
> * Add rb_root root_net_port.
> 
> Changes since v4:
> * Refactoring landlock_create_ruleset() - splits ruleset and
> masks checks.
> * Refactoring landlock_create_ruleset() and landlock mask
> setters/getters to support two rule types.
> * Refactoring landlock_add_rule syscall add_rule_path_beneath
> function by factoring out get_ruleset_from_fd() and
> landlock_put_ruleset().
> 
> ---
>   security/landlock/limits.h   |  8 +++-
>   security/landlock/ruleset.c  | 82 +++++++++++++++++++++++++++++++-----
>   security/landlock/ruleset.h  | 34 +++++++++++++--
>   security/landlock/syscalls.c | 45 +++++++++++---------
>   4 files changed, 132 insertions(+), 37 deletions(-)
> 
> diff --git a/security/landlock/limits.h b/security/landlock/limits.h
> index b54184ab9439..23694bf05cb7 100644
> --- a/security/landlock/limits.h
> +++ b/security/landlock/limits.h
> @@ -22,6 +22,12 @@
>   #define LANDLOCK_MASK_ACCESS_FS		((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
>   #define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
> 
> -/* clang-format on */
> +#define LANDLOCK_LAST_ACCESS_NET	LANDLOCK_ACCESS_NET_CONNECT_TCP
> +#define LANDLOCK_MASK_ACCESS_NET	((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
> +#define LANDLOCK_NUM_ACCESS_NET		__const_hweight64(LANDLOCK_MASK_ACCESS_NET)
> +#define LANDLOCK_MASK_SHIFT_NET		16
> +
> +#define LANDLOCK_RULE_TYPE_NUM		LANDLOCK_RULE_NET_SERVICE
> 
> +/* clang-format on */
>   #endif /* _SECURITY_LANDLOCK_LIMITS_H */
> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
> index c4ed783d655b..ea9ecb3f471a 100644
> --- a/security/landlock/ruleset.c
> +++ b/security/landlock/ruleset.c
> @@ -36,6 +36,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
>   	refcount_set(&new_ruleset->usage, 1);
>   	mutex_init(&new_ruleset->lock);
>   	new_ruleset->root_inode = RB_ROOT;
> +	new_ruleset->root_net_port = RB_ROOT;
>   	new_ruleset->num_layers = num_layers;
>   	/*
>   	 * hierarchy = NULL
> @@ -46,17 +47,21 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
>   }
> 
>   struct landlock_ruleset *landlock_create_ruleset(
> -		const access_mask_t access_mask)
> +					const access_mask_t access_mask_fs,
> +					const access_mask_t access_mask_net)
>   {
>   	struct landlock_ruleset *new_ruleset;
> 
>   	/* Informs about useless ruleset. */
> -	if (!access_mask)
> +	if (!access_mask_fs && !access_mask_net)
>   		return ERR_PTR(-ENOMSG);
>   	new_ruleset = create_ruleset(1);
> -	if (!IS_ERR(new_ruleset))
> -		landlock_set_fs_access_mask(new_ruleset, access_mask, 0);
> -
> +	if (IS_ERR(new_ruleset))
> +		return new_ruleset;
> +	if (access_mask_fs)
> +		landlock_set_fs_access_mask(new_ruleset, access_mask_fs, 0);
> +	if (access_mask_net)
> +		landlock_set_net_access_mask(new_ruleset, access_mask_net, 0);
>   	return new_ruleset;
>   }
> 
> @@ -94,9 +99,11 @@ static struct landlock_rule *create_rule(
>   		return ERR_PTR(-ENOMEM);
>   	RB_CLEAR_NODE(&new_rule->node);
> 
> -	if (object_ptr) {
> +	if (object_ptr && !object_data) {
>   		landlock_get_object(object_ptr);
>   		new_rule->object.ptr = object_ptr;
> +	} else if (object_data && !object_ptr) {
> +		new_rule->object.data = object_data;
>   	} else if (object_ptr && object_data) {
>   		WARN_ON_ONCE(1);
>   		return ERR_PTR(-EINVAL);
> @@ -132,10 +139,12 @@ static void build_check_ruleset(void)
>   		.num_layers = ~0,
>   	};
>   	typeof(ruleset.access_masks[0]) fs_access_mask = ~0;
> +	typeof(ruleset.access_masks[0]) net_access_mask = ~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(net_access_mask < LANDLOCK_MASK_ACCESS_NET);
>   }
> 
>   /**
> @@ -183,6 +192,11 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
>   		object_data = (uintptr_t)object_ptr;
>   		root = &ruleset->root_inode;
>   		break;
> +	case LANDLOCK_RULE_NET_SERVICE:
> +		if (WARN_ON_ONCE(object_ptr))
> +			return -EINVAL;
> +		root = &ruleset->root_net_port;
> +		break;
>   	default:
>   		WARN_ON_ONCE(1);
>   		return -EINVAL;
> @@ -237,6 +251,16 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
>   					&ruleset->root_inode);
>   			free_rule(this, rule_type);
>   			break;
> +		case LANDLOCK_RULE_NET_SERVICE:
> +			new_rule = create_rule(NULL, object_data,
> +					       &this->layers, this->num_layers,
> +					       &(*layers)[0]);
> +			if (IS_ERR(new_rule))
> +				return PTR_ERR(new_rule);
> +			rb_replace_node(&this->node, &new_rule->node,
> +					&ruleset->root_net_port);
> +			free_rule(this, rule_type);
> +			break;
>   		}
>   		return 0;
>   	}
> @@ -254,6 +278,15 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
>   		rb_link_node(&new_rule->node, parent_node, walker_node);
>   		rb_insert_color(&new_rule->node, &ruleset->root_inode);
>   		break;
> +	case LANDLOCK_RULE_NET_SERVICE:
> +		new_rule = create_rule(NULL, object_data, layers,
> +				       num_layers, NULL);
> +		if (IS_ERR(new_rule))
> +			return PTR_ERR(new_rule);
> +		rb_link_node(&new_rule->node, parent_node, walker_node);
> +		rb_insert_color(&new_rule->node, &ruleset->root_net_port);
> +		ruleset->num_rules++;
> +		break;
>   	}
>   	return 0;
>   }
> @@ -315,6 +348,9 @@ static int tree_merge(struct landlock_ruleset *const src,
>   	case LANDLOCK_RULE_PATH_BENEATH:
>   		src_root = &src->root_inode;
>   		break;
> +	case LANDLOCK_RULE_NET_SERVICE:
> +		src_root = &src->root_net_port;
> +		break;
>   	default:
>   		return -EINVAL;
>   	}
> @@ -341,6 +377,11 @@ static int tree_merge(struct landlock_ruleset *const src,
>   					  rule_type, &layers,
>   					  ARRAY_SIZE(layers));
>   			break;
> +		case LANDLOCK_RULE_NET_SERVICE:
> +			err = insert_rule(dst, NULL, walker_rule->object.data,
> +					  rule_type, &layers,
> +					  ARRAY_SIZE(layers));
> +			break;
>   		}
>   		if (err)
>   			return err;
> @@ -376,6 +417,10 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>   	err = tree_merge(src, dst, LANDLOCK_RULE_PATH_BENEATH);
>   	if (err)
>   		goto out_unlock;
> +	/* Merges the @src network tree. */
> +	err = tree_merge(src, dst, LANDLOCK_RULE_NET_SERVICE);
> +	if (err)
> +		goto out_unlock;
> 
>   out_unlock:
>   	mutex_unlock(&src->lock);
> @@ -395,6 +440,9 @@ static int tree_copy(struct landlock_ruleset *const parent,
>   	case LANDLOCK_RULE_PATH_BENEATH:
>   		parent_root = &parent->root_inode;
>   		break;
> +	case LANDLOCK_RULE_NET_SERVICE:
> +		parent_root = &parent->root_net_port;
> +		break;
>   	default:
>   		return -EINVAL;
>   	}
> @@ -407,6 +455,12 @@ static int tree_copy(struct landlock_ruleset *const parent,
>   					  rule_type, &walker_rule->layers,
>   					  walker_rule->num_layers);
>   			break;
> +		case LANDLOCK_RULE_NET_SERVICE:
> +			err = insert_rule(child, NULL,
> +					  walker_rule->object.data, rule_type,
> +					  &walker_rule->layers,
> +					  walker_rule->num_layers);
> +			break;
>   		}
>   		if (err)
>   			return err;
> @@ -429,6 +483,10 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
> 
>   	/* Copies the @parent inode tree. */
>   	err = tree_copy(parent, child, LANDLOCK_RULE_PATH_BENEATH);
> +	if (err)
> +		goto out_unlock;
> +	/* Copies the @parent inode tree. */

Not the inode tree this time.


> +	err = tree_copy(parent, child, LANDLOCK_RULE_NET_SERVICE);
>   	if (err)
>   		goto out_unlock;
> 
> @@ -463,9 +521,11 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
> 
>   	might_sleep();
>   	rbtree_postorder_for_each_entry_safe(freeme, next,
> -					     &ruleset->root_inode,
> -					     node)
> +					     &ruleset->root_inode, node)
>   		free_rule(freeme, LANDLOCK_RULE_PATH_BENEATH);
> +	rbtree_postorder_for_each_entry_safe(freeme, next,
> +					     &ruleset->root_net_port, node)
> +		free_rule(freeme, LANDLOCK_RULE_NET_SERVICE);
>   	put_hierarchy(ruleset->hierarchy);
>   	kfree(ruleset);
>   }
> @@ -560,13 +620,13 @@ const struct landlock_rule *landlock_find_rule(
>   {
>   	const struct rb_node *node;
> 
> -	if (!object_data)
> -		return NULL;
> -
>   	switch (rule_type) {
>   	case LANDLOCK_RULE_PATH_BENEATH:
>   		node = ruleset->root_inode.rb_node;
>   		break;
> +	case LANDLOCK_RULE_NET_SERVICE:
> +		node = ruleset->root_net_port.rb_node;
> +		break;
>   	default:
>   		WARN_ON_ONCE(1);
>   		return NULL;
> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
> index f3cd890d0348..916b30b31c06 100644
> --- a/security/landlock/ruleset.h
> +++ b/security/landlock/ruleset.h
> @@ -102,6 +102,12 @@ struct landlock_ruleset {
>   	 * tree is immutable until @usage reaches zero.
>   	 */
>   	struct rb_root root_inode;
> +	/**
> +	 * @root_net_port: Root of a red-black tree containing object nodes
> +	 * for network port. Once a ruleset is tied to a process (i.e. as a domain),
> +	 * this tree is immutable until @usage reaches zero.
> +	 */
> +	struct rb_root root_net_port;
>   	/**
>   	 * @hierarchy: Enables hierarchy identification even when a parent
>   	 * domain vanishes.  This is needed for the ptrace protection.
> @@ -157,7 +163,8 @@ struct landlock_ruleset {
>   };
> 
>   struct landlock_ruleset *landlock_create_ruleset(
> -		const access_mask_t access_mask);
> +					const access_mask_t access_mask_fs,
> +					const access_mask_t access_mask_net);
> 
>   void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
>   void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
> @@ -183,11 +190,12 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
>   }
> 
>   /* A helper function to set a filesystem mask */
> -static inline void landlock_set_fs_access_mask(struct landlock_ruleset *ruleset,
> -				 const access_mask_t access_maskset,
> +static inline void landlock_set_fs_access_mask(
> +				 struct landlock_ruleset *ruleset,
> +				 const access_mask_t access_mask_fs,
>   				 u16 mask_level)
>   {
> -	ruleset->access_masks[mask_level] = access_maskset;
> +	ruleset->access_masks[mask_level] = access_mask_fs;
>   }
> 
>   /* A helper function to get a filesystem mask */
> @@ -198,6 +206,24 @@ static inline u32 landlock_get_fs_access_mask(
>   	return (ruleset->access_masks[mask_level] & LANDLOCK_MASK_ACCESS_FS);
>   }
> 
> +/* A helper function to set a network mask */
> +static inline void landlock_set_net_access_mask(
> +				  struct landlock_ruleset *ruleset,
> +				  const access_mask_t access_mask_net,
> +				  u16 mask_level)
> +{
> +	ruleset->access_masks[mask_level] |= (access_mask_net <<
> +					      LANDLOCK_MASK_SHIFT_NET);
> +}
> +
> +/* A helper function to get a network mask */
> +static inline u32 landlock_get_net_access_mask(
> +				const struct landlock_ruleset *ruleset,
> +				u16 mask_level)
> +{
> +	return (ruleset->access_masks[mask_level] >> LANDLOCK_MASK_SHIFT_NET);
> +}
> +
>   access_mask_t get_handled_accesses(
>   		const struct landlock_ruleset *const domain,
>   		u16 rule_type, u16 num_access);
> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> index 31f9facec123..812541f4e155 100644
> --- a/security/landlock/syscalls.c
> +++ b/security/landlock/syscalls.c
> @@ -189,8 +189,14 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
>   	    LANDLOCK_MASK_ACCESS_FS)
>   		return -EINVAL;
> 
> +	/* Checks network content (and 32-bits cast). */
> +	if ((ruleset_attr.handled_access_net | LANDLOCK_MASK_ACCESS_NET) !=
> +			LANDLOCK_MASK_ACCESS_NET)
> +		return -EINVAL;
> +
>   	/* Checks arguments and transforms to kernel struct. */
> -	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs);
> +	ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs,
> +					  ruleset_attr.handled_access_net);
>   	if (IS_ERR(ruleset))
>   		return PTR_ERR(ruleset);
> 
> @@ -275,21 +281,17 @@ static int get_path_from_fd(const s32 fd, struct path *const path)
>   	return err;
>   }
> 
> -static int add_rule_path_beneath(const int ruleset_fd, const void *const rule_attr)
> +static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
> +				 const void *const rule_attr)
>   {
>   	struct landlock_path_beneath_attr path_beneath_attr;
>   	struct path path;
> -	struct landlock_ruleset *ruleset;
>   	int res, err;
> -
> -	/* Gets and checks the ruleset. */
> -	ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_WRITE);
> -	if (IS_ERR(ruleset))
> -		return PTR_ERR(ruleset);
> +	u32 mask;
> 
>   	/* Copies raw user space buffer, only one type for now. */
>   	res = copy_from_user(&path_beneath_attr, rule_attr,
> -				sizeof(path_beneath_attr));
> +			sizeof(path_beneath_attr));
>   	if (res)
>   		return -EFAULT;
> 
> @@ -298,32 +300,26 @@ static int add_rule_path_beneath(const int ruleset_fd, const void *const rule_at
>   	 * are ignored in path walks.
>   	 */
>   	if (!path_beneath_attr.allowed_access) {
> -		err = -ENOMSG;
> -		goto out_put_ruleset;
> +		return -ENOMSG;
>   	}
>   	/*
>   	 * Checks that allowed_access matches the @ruleset constraints
>   	 * (ruleset->access_masks[0] is automatically upgraded to 64-bits).
>   	 */
> -	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;
> -	}
> +	mask = landlock_get_fs_access_mask(ruleset, 0);
> +	if ((path_beneath_attr.allowed_access | mask) != mask)
> +		return -EINVAL;
> 
>   	/* Gets and checks the new rule. */
>   	err = get_path_from_fd(path_beneath_attr.parent_fd, &path);
>   	if (err)
> -		goto out_put_ruleset;
> +		return err;
> 
>   	/* Imports the new rule. */
>   	err = landlock_append_fs_rule(ruleset, &path,
>   				      path_beneath_attr.allowed_access);
>   	path_put(&path);
> 
> -out_put_ruleset:
> -	landlock_put_ruleset(ruleset);
>   	return err;
>   }
> 
> @@ -360,6 +356,7 @@ SYSCALL_DEFINE4(landlock_add_rule,
>   		const int, ruleset_fd, const enum landlock_rule_type, rule_type,
>   		const void __user *const, rule_attr, const __u32, flags)
>   {
> +	struct landlock_ruleset *ruleset;
>   	int err;
> 
>   	if (!landlock_initialized)
> @@ -369,14 +366,20 @@ SYSCALL_DEFINE4(landlock_add_rule,
>   	if (flags)
>   		return -EINVAL;
> 
> +	/* Gets and checks the ruleset. */
> +	ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_WRITE);
> +	if (IS_ERR(ruleset))
> +		return PTR_ERR(ruleset);

This shouldn't be part of this patch.


> +
>   	switch (rule_type) {
>   	case LANDLOCK_RULE_PATH_BENEATH:
> -		err = add_rule_path_beneath(ruleset_fd, rule_attr);
> +		err = add_rule_path_beneath(ruleset, rule_attr);
>   		break;
>   	default:
>   		err = -EINVAL;
>   		break;
>   	}
> +	landlock_put_ruleset(ruleset);
>   	return err;
>   }
> 
> --
> 2.25.1
> 

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