Re: [PATCH v7 08/18] landlock: add network rules support

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

9/6/2022 11:08 AM, Mickaël Salaün пишет:
> On 29/08/2022 19:03, Konstantin Meskhidze wrote:
> > This commit adds network rules support in internal landlock functions
> > (presented in ruleset.c) and landlock_create_ruleset syscall.
> >
> > Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
> > ---
> >
> > Changes since v6:
> > * Renames landlock_set_net_access_mask() to landlock_add_net_access_mask()
> >    because it OR values.
> > * Makes landlock_add_net_access_mask() more resilient incorrect values.
> > * Refactors landlock_get_net_access_mask().
> > * Renames LANDLOCK_MASK_SHIFT_NET to LANDLOCK_SHIFT_ACCESS_NET and use
> >    LANDLOCK_NUM_ACCESS_FS as value.
> > * Updates access_masks_t to u32 to support network access actions.
> > * Refactors landlock internal functions to support network actions with
> >    landlock_key/key_type/id types.
> >
> > Changes since v5:
> > * Gets rid of partial revert from landlock_add_rule
> > syscall.
> > * Formats code with clang-format-14.
> >
> > Changes since v4:
> > * Refactors landlock_create_ruleset() - splits ruleset and
> > masks checks.
> > * Refactors landlock_create_ruleset() and landlock mask
> > setters/getters to support two rule types.
> > * Refactors landlock_add_rule syscall add_rule_path_beneath
> > function by factoring out get_ruleset_from_fd() and
> > landlock_put_ruleset().
> >
> > Changes since v3:
> > * Splits commit.
> > * Adds network rule support for internal landlock functions.
> > * Adds set_mask and get_mask for network.
> > * Adds rb_root root_net_port.
> >
> > ---
> >   security/landlock/limits.h   |  6 +++++-
> >   security/landlock/ruleset.c  | 38 +++++++++++++++++++++++++++++----
> >   security/landlock/ruleset.h  | 41 ++++++++++++++++++++++++++++++++++--
> >   security/landlock/syscalls.c |  8 ++++++-
> >   4 files changed, 85 insertions(+), 8 deletions(-)
> >
> > diff --git a/security/landlock/limits.h b/security/landlock/limits.h
> > index bafb3b8dc677..8a1a6463c64e 100644
> > --- a/security/landlock/limits.h
> > +++ b/security/landlock/limits.h
> > @@ -23,6 +23,10 @@
> >   #define LANDLOCK_NUM_ACCESS_FS		__const_hweight64(LANDLOCK_MASK_ACCESS_FS)
> >   #define LANDLOCK_SHIFT_ACCESS_FS	0
> >
> > -/* 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_SHIFT_ACCESS_NET	LANDLOCK_NUM_ACCESS_FS
> >
> > +/* clang-format on */
> >   #endif /* _SECURITY_LANDLOCK_LIMITS_H */
> > diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
> > index 84fcd8eb30d4..442f212039df 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
> > @@ -46,16 +47,21 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
> >   }
> >
> >   struct landlock_ruleset *
> > -landlock_create_ruleset(const access_mask_t fs_access_mask)
> > +landlock_create_ruleset(const access_mask_t fs_access_mask,
> > +			const access_mask_t net_access_mask)
> >   {
> >   	struct landlock_ruleset *new_ruleset;
> >
> >   	/* Informs about useless ruleset. */
> > -	if (!fs_access_mask)
> > +	if (!fs_access_mask && !net_access_mask)
> >   		return ERR_PTR(-ENOMSG);
> >   	new_ruleset = create_ruleset(1);
> > -	if (!IS_ERR(new_ruleset))
> > +	if (IS_ERR(new_ruleset))
> > +		return new_ruleset;
> > +	if (fs_access_mask)
> >   		landlock_add_fs_access_mask(new_ruleset, fs_access_mask, 0);
> > +	if (net_access_mask)
> > +		landlock_add_net_access_mask(new_ruleset, net_access_mask, 0);
> >   	return new_ruleset;
> >   }
> >
> > @@ -73,6 +79,8 @@ static inline bool is_object_pointer(const enum landlock_key_type key_type)
> >   	switch (key_type) {
> >   	case LANDLOCK_KEY_INODE:
> >   		return true;
> > +	case LANDLOCK_KEY_NET_PORT:
> > +		return false;
> >   	}
> >   	WARN_ON_ONCE(1);
> >   	return false;
> > @@ -126,6 +134,9 @@ static inline struct rb_root *get_root(struct landlock_ruleset *const ruleset,
> >   	case LANDLOCK_KEY_INODE:
> >   		root = &ruleset->root_inode;
> >   		break;
> > +	case LANDLOCK_KEY_NET_PORT:
> > +		root = &ruleset->root_net_port;
> > +		break;
> >   	}
> >   	if (WARN_ON_ONCE(!root))
> >   		return ERR_PTR(-EINVAL);
> > @@ -154,7 +165,9 @@ static void build_check_ruleset(void)
> >   	BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
> >   	BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
> >   	BUILD_BUG_ON(access_masks <
> > -		     (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS));
> > +		     (LANDLOCK_MASK_ACCESS_FS << LANDLOCK_SHIFT_ACCESS_FS) +
> > +			     (LANDLOCK_MASK_ACCESS_NET
> > +			      << LANDLOCK_SHIFT_ACCESS_NET));
> >   }
> >
> >   /**
> > @@ -367,6 +380,11 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
> >   	if (err)
> >   		goto out_unlock;
> >
> > +	/* Merges the @src network port tree. */
> > +	err = merge_tree(dst, src, LANDLOCK_KEY_NET_PORT);
> > +	if (err)
> > +		goto out_unlock;
> > +
> >   out_unlock:
> >   	mutex_unlock(&src->lock);
> >   	mutex_unlock(&dst->lock);
> > @@ -419,6 +437,11 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
> >   	if (err)
> >   		goto out_unlock;
> >
> > +	/* Copies the @parent network port tree. */
> > +	err = inherit_tree(parent, child, LANDLOCK_KEY_NET_PORT);
> > +	if (err)
> > +		goto out_unlock;
> > +
> >   	if (WARN_ON_ONCE(child->num_layers <= parent->num_layers)) {
> >   		err = -EINVAL;
> >   		goto out_unlock;
> > @@ -451,6 +474,9 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
> >   	rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
> >   					     node)
> >   		free_rule(freeme, LANDLOCK_KEY_INODE);
> > +	rbtree_postorder_for_each_entry_safe(freeme, next,
> > +					     &ruleset->root_net_port, node)
> > +		free_rule(freeme, LANDLOCK_KEY_NET_PORT);
> >   	put_hierarchy(ruleset->hierarchy);
> >   	kfree(ruleset);
> >   }
> > @@ -640,6 +666,10 @@ access_mask_t init_layer_masks(const struct landlock_ruleset *const domain,
> >   		get_access_mask = landlock_get_fs_access_mask;
> >   		num_access = LANDLOCK_NUM_ACCESS_FS;
> >   		break;
> > +	case LANDLOCK_KEY_NET_PORT:
> > +		get_access_mask = landlock_get_net_access_mask;
> > +		num_access = LANDLOCK_NUM_ACCESS_NET;
> > +		break;
> >   	default:
> >   		WARN_ON_ONCE(1);
> >   		return 0;
> > diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
> > index 2083855bf42d..d456ee90b648 100644
> > --- a/security/landlock/ruleset.h
> > +++ b/security/landlock/ruleset.h
> > @@ -26,7 +26,7 @@ static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
> >   static_assert(sizeof(unsigned long) >= sizeof(access_mask_t));
> >
> >   /* Ruleset access masks. */
> > -typedef u16 access_masks_t;
> > +typedef u32 access_masks_t;
> >   /* Makes sure all ruleset access rights can be stored. */
> >   static_assert(BITS_PER_TYPE(access_masks_t) >= LANDLOCK_NUM_ACCESS_FS);
>
> There is some fixes missing from my patch.
>
>
> > @@ -66,6 +66,11 @@ enum landlock_key_type {
> >   	 * keys.
> >   	 */
> >   	LANDLOCK_KEY_INODE = 1,
>
>
> #if IS_ENABLED(CONFIG_INET)
>
> > +	/**
> > +	 * @LANDLOCK_KEY_NET_PORT: Type of &landlock_ruleset.root_net_port's
> > +	 * node keys.
> > +	 */
> > +	LANDLOCK_KEY_NET_PORT = 2,
>
> #endif /* IS_ENABLED(CONFIG_INET) */
>
> And then all use of LANDLOCK_KEY_NET_PORT should be surrounded by the
> same check (but not directly in the net.c file).

 I checked the branch with your patches: tmp-net 
(7d6cf40a6f81adf607ad3cc17aaa11e256beeea4), but I did not find #if 
IS_ENABLED(CONFIG_INET) surrounding LANDLOCK_KEY_NET_PORT.
> >   };
> >
> >   /**
> > @@ -133,6 +138,12 @@ struct landlock_ruleset {
> >   	 * reaches zero.
> >   	 */
> >   	struct rb_root root_inode;
>
> #if IS_ENABLED(CONFIG_INET)
>
> > +	/**
> > +	 * @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.
> > +	 */
>
> There is some fixes missing from my patch. Please explain everything
> that you didn't take.

   Sorry. I did merge your patch manually and did not tell the 
difference here. Will be fixed
> > +	struct rb_root root_net_port;
>
>
> #endif /* IS_ENABLED(CONFIG_INET) */
>
> And then all use of root_net_port should be surrounded by the same check.

  The same - I did not find #if IS_ENABLED(CONFIG_INET) surrounding 
root_net_port in tmp-net (7d6cf40a6f81adf607ad3cc17aaa11e256beeea4)
> I think it should be OK to keep all other remaining network references
> though (e.g. access_masks and the ).

  Ok. Thanks.
> >   	/**
> >   	 * @hierarchy: Enables hierarchy identification even when a parent
> >   	 * domain vanishes.  This is needed for the ptrace protection.
> > @@ -188,7 +199,8 @@ struct landlock_ruleset {
> >   };
> >
> >   struct landlock_ruleset *
> > -landlock_create_ruleset(const access_mask_t access_mask);
> > +landlock_create_ruleset(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);
> > @@ -226,6 +238,21 @@ landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
> >   		(fs_mask << LANDLOCK_SHIFT_ACCESS_FS);
> >   }
> >
> > +/* A helper function to set a network mask. */
>
> I already said that this comment is useless, and I removed it in my
> patch. Please take a closer look at reviews.

 Sorry. I missed that in your patch. Will be fixed.
> > +static inline void
> > +landlock_add_net_access_mask(struct landlock_ruleset *const ruleset,
> > +			     const access_mask_t net_access_mask,
> > +			     const u16 layer_level)
> > +{
> > +	access_mask_t net_mask = net_access_mask & LANDLOCK_MASK_ACCESS_NET;
> > +
> > +	/* Should already be checked in sys_landlock_create_ruleset(). */
> > +	WARN_ON_ONCE(net_access_mask != net_mask);
> > +	// TODO: Add tests to check "|=" and not "="
> > +	ruleset->access_masks[layer_level] |=
> > +		(net_mask << LANDLOCK_SHIFT_ACCESS_NET);
> > +}
> > +
> >   /* A helper function to get a filesystem mask. */
> >   static inline access_mask_t
> >   landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
> > @@ -236,6 +263,16 @@ landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
> >   	       LANDLOCK_MASK_ACCESS_FS;
> >   }
> >
> > +/* A helper function to get a network mask. */
> > +static inline access_mask_t
> > +landlock_get_net_access_mask(const struct landlock_ruleset *const ruleset,
> > +			     const u16 layer_level)
> > +{
> > +	return (ruleset->access_masks[layer_level] >>
> > +		LANDLOCK_SHIFT_ACCESS_NET) &
> > +	       LANDLOCK_MASK_ACCESS_NET;
> > +}
> > +
>
> This hunk doesn't match my patch.

  Do you mean landlock_get_net_access_mask? If yes, there is no diff 
with your patch here.
> >   bool unmask_layers(const struct landlock_rule *const rule,
> >   		   const access_mask_t access_request,
> >   		   layer_mask_t (*const layer_masks)[],
> > diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> > index ffd5805eddd9..641155f6f6f8 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);
> >
> > --
> > 2.25.1
> .