[PATCH v4 0/3] Refactor Landlock access mask management

[PATCH v4 0/3] Refactor Landlock access mask management

[Mickaël Salaün]

Hi,

To simplify code for new access types [1], add 2 new helpers:
- landlock_union_access_masks()
- landlock_get_applicable_domain()

This fourth version mainly rename these helpers.

The last patch uses these helpers to optimize Landlock scope management
like with filesystem and network access checks.

[1] https://lore.kernel.org/r/3433b163-2371-e679-cc8a-e540a0218bca@huawei-partners.com

Previous version:
v3: https://lore.kernel.org/r/20241022151144.872797-2-mic@digikod.net
v2: https://lore.kernel.org/r/20241014124835.1152246-1-mic@digikod.net
v1: https://lore.kernel.org/r/20241001141234.397649-1-mic@digikod.net

Regards,

Mickaël Salaün (3):
  landlock: Refactor filesystem access mask management
  landlock: Refactor network access mask management
  landlock: Optimize scope enforcement

 security/landlock/fs.c       | 31 ++++-----------
 security/landlock/net.c      | 28 +++-----------
 security/landlock/ruleset.h  | 73 ++++++++++++++++++++++++++++++++----
 security/landlock/syscalls.c |  2 +-
 security/landlock/task.c     | 18 +++++++--
 5 files changed, 95 insertions(+), 57 deletions(-)


base-commit: dad2f20715163e80aab284fb092efc8c18bf97c7
-- 
2.47.0

[PATCH v4 1/3] landlock: Refactor filesystem access mask management

[Mickaël Salaün]

Replace get_raw_handled_fs_accesses() with a generic
landlock_merge_access_masks(), and replace get_fs_domain() with a
generic landlock_match_ruleset().  These helpers will also be useful for
other types of access.

Cc: Günther Noack <gnoack@google.com>
Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net
---

Changes since v3:
* Rename landlock_merge_access_masks() to landlock_union_access_masks(),
  suggested by Günther.
* Rename landlock_match_ruleset() to landlock_get_applicable_domain(),
  suggested by Günther.
* Rename the "ruleset" arguments to "domain" for consistency with these
  new helpers.
* Use typeof_member(), suggested by Günther.  Also include kernel.h
  (instead of the new container_of.h to ease backports).

Changes since v2:
* Create a new type union access_masks_all instead of changing struct
  acces_masks.
* Replace get_fs_domain() with an explicit call to
  landlock_match_ruleset().

Changes since v1:
* Rename landlock_filter_access_masks() to landlock_match_ruleset().
* Rename local variables from domain to ruleset to mach helpers'
  semantic.  We'll rename and move these helpers when we'll have a
  dedicated domain struct type.
* Rename the all_fs mask to any_fs.
* Add documentation, as suggested by Günther.
---
 security/landlock/fs.c       | 31 ++++-----------
 security/landlock/ruleset.h  | 73 ++++++++++++++++++++++++++++++++----
 security/landlock/syscalls.c |  2 +-
 3 files changed, 74 insertions(+), 32 deletions(-)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 7d79fc8abe21..e31b97a9f175 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -388,38 +388,22 @@ static bool is_nouser_or_private(const struct dentry *dentry)
 		unlikely(IS_PRIVATE(d_backing_inode(dentry))));
 }
 
-static access_mask_t
-get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain)
-{
-	access_mask_t access_dom = 0;
-	size_t layer_level;
-
-	for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
-		access_dom |=
-			landlock_get_raw_fs_access_mask(domain, layer_level);
-	return access_dom;
-}
-
 static access_mask_t
 get_handled_fs_accesses(const struct landlock_ruleset *const domain)
 {
 	/* Handles all initially denied by default access rights. */
-	return get_raw_handled_fs_accesses(domain) |
+	return landlock_union_access_masks(domain).fs |
 	       LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
 }
 
-static const struct landlock_ruleset *
-get_fs_domain(const struct landlock_ruleset *const domain)
-{
-	if (!domain || !get_raw_handled_fs_accesses(domain))
-		return NULL;
-
-	return domain;
-}
+static const struct access_masks any_fs = {
+	.fs = ~0,
+};
 
 static const struct landlock_ruleset *get_current_fs_domain(void)
 {
-	return get_fs_domain(landlock_get_current_domain());
+	return landlock_get_applicable_domain(landlock_get_current_domain(),
+					      any_fs);
 }
 
 /*
@@ -1517,7 +1501,8 @@ static int hook_file_open(struct file *const file)
 	access_mask_t open_access_request, full_access_request, allowed_access,
 		optional_access;
 	const struct landlock_ruleset *const dom =
-		get_fs_domain(landlock_cred(file->f_cred)->domain);
+		landlock_get_applicable_domain(
+			landlock_cred(file->f_cred)->domain, any_fs);
 
 	if (!dom)
 		return 0;
diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 61bdbc550172..698fa3114cf4 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h
@@ -11,6 +11,7 @@
 
 #include <linux/bitops.h>
 #include <linux/build_bug.h>
+#include <linux/kernel.h>
 #include <linux/mutex.h>
 #include <linux/rbtree.h>
 #include <linux/refcount.h>
@@ -47,6 +48,15 @@ struct access_masks {
 	access_mask_t scope : LANDLOCK_NUM_SCOPE;
 };
 
+union access_masks_all {
+	struct access_masks masks;
+	u32 all;
+};
+
+/* Makes sure all fields are covered. */
+static_assert(sizeof(typeof_member(union access_masks_all, masks)) ==
+	      sizeof(typeof_member(union access_masks_all, all)));
+
 typedef u16 layer_mask_t;
 /* Makes sure all layers can be checked. */
 static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
@@ -260,6 +270,60 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
 		refcount_inc(&ruleset->usage);
 }
 
+/**
+ * landlock_union_access_masks - Return all access rights handled in the
+ *				 domain
+ *
+ * @domain: Landlock ruleset (used as a domain)
+ *
+ * Returns: an access_masks result of the OR of all the domain's access masks.
+ */
+static inline struct access_masks
+landlock_union_access_masks(const struct landlock_ruleset *const domain)
+{
+	union access_masks_all matches = {};
+	size_t layer_level;
+
+	for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
+		union access_masks_all layer = {
+			.masks = domain->access_masks[layer_level],
+		};
+
+		matches.all |= layer.all;
+	}
+
+	return matches.masks;
+}
+
+/**
+ * landlock_get_applicable_domain - Return @domain if it applies to (handles)
+ *				    the access rights specified in @masks
+ *
+ * @domain: Landlock ruleset (used as a domain)
+ * @masks: access masks
+ *
+ * Returns: @domain if any access rights specified in @masks is handled, or
+ * NULL otherwise.
+ */
+static inline const struct landlock_ruleset *
+landlock_get_applicable_domain(const struct landlock_ruleset *const domain,
+			       const struct access_masks masks)
+{
+	const union access_masks_all masks_all = {
+		.masks = masks,
+	};
+	union access_masks_all merge = {};
+
+	if (!domain)
+		return NULL;
+
+	merge.masks = landlock_union_access_masks(domain);
+	if (merge.all & masks_all.all)
+		return domain;
+
+	return NULL;
+}
+
 static inline void
 landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
 			    const access_mask_t fs_access_mask,
@@ -295,19 +359,12 @@ landlock_add_scope_mask(struct landlock_ruleset *const ruleset,
 	ruleset->access_masks[layer_level].scope |= mask;
 }
 
-static inline access_mask_t
-landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset,
-				const u16 layer_level)
-{
-	return ruleset->access_masks[layer_level].fs;
-}
-
 static inline access_mask_t
 landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
 			    const u16 layer_level)
 {
 	/* Handles all initially denied by default access rights. */
-	return landlock_get_raw_fs_access_mask(ruleset, layer_level) |
+	return ruleset->access_masks[layer_level].fs |
 	       LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
 }
 
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index f5a0e7182ec0..c097d356fa45 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -329,7 +329,7 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
 		return -ENOMSG;
 
 	/* Checks that allowed_access matches the @ruleset constraints. */
-	mask = landlock_get_raw_fs_access_mask(ruleset, 0);
+	mask = ruleset->access_masks[0].fs;
 	if ((path_beneath_attr.allowed_access | mask) != mask)
 		return -EINVAL;
 
-- 
2.47.0

Re: [PATCH v4 1/3] landlock: Refactor filesystem access mask management

[Mickaël Salaün]

On Sat, Nov 09, 2024 at 12:08:54PM +0100, Mickaël Salaün wrote:
> Replace get_raw_handled_fs_accesses() with a generic
> landlock_merge_access_masks(), and replace get_fs_domain() with a
> generic landlock_match_ruleset().  These helpers will also be useful for
> other types of access.

Of course I need to update the commit messages with the new names...

> 
> Cc: Günther Noack <gnoack@google.com>
> Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net

Re: [PATCH v4 1/3] landlock: Refactor filesystem access mask management

[Günther Noack]

On Sat, Nov 09, 2024 at 12:14:49PM +0100, Mickaël Salaün wrote:
> On Sat, Nov 09, 2024 at 12:08:54PM +0100, Mickaël Salaün wrote:
> > Replace get_raw_handled_fs_accesses() with a generic
> > landlock_merge_access_masks(), and replace get_fs_domain() with a
> > generic landlock_match_ruleset().  These helpers will also be useful for
> > other types of access.
> 
> Of course I need to update the commit messages with the new names...

Yes, those are still using the old function names.

At this point my other two remaining remarks are so minor,
I think we can skip another version of this patch set. 👍

Thanks for simplifying the code!

—Günther

Re: [PATCH v4 1/3] landlock: Refactor filesystem access mask management

[Günther Noack]

On Sat, Nov 09, 2024 at 12:08:54PM +0100, Mickaël Salaün wrote:
> Replace get_raw_handled_fs_accesses() with a generic
> landlock_merge_access_masks(), and replace get_fs_domain() with a
> generic landlock_match_ruleset().  These helpers will also be useful for
> other types of access.
> 
> Cc: Günther Noack <gnoack@google.com>
> Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> Link: https://lore.kernel.org/r/20241109110856.222842-2-mic@digikod.net
> ---
> 
> Changes since v3:
> * Rename landlock_merge_access_masks() to landlock_union_access_masks(),
>   suggested by Günther.
> * Rename landlock_match_ruleset() to landlock_get_applicable_domain(),
>   suggested by Günther.
> * Rename the "ruleset" arguments to "domain" for consistency with these
>   new helpers.
> * Use typeof_member(), suggested by Günther.  Also include kernel.h
>   (instead of the new container_of.h to ease backports).
> 
> Changes since v2:
> * Create a new type union access_masks_all instead of changing struct
>   acces_masks.
> * Replace get_fs_domain() with an explicit call to
>   landlock_match_ruleset().
> 
> Changes since v1:
> * Rename landlock_filter_access_masks() to landlock_match_ruleset().
> * Rename local variables from domain to ruleset to mach helpers'
>   semantic.  We'll rename and move these helpers when we'll have a
>   dedicated domain struct type.
> * Rename the all_fs mask to any_fs.
> * Add documentation, as suggested by Günther.
> ---
>  security/landlock/fs.c       | 31 ++++-----------
>  security/landlock/ruleset.h  | 73 ++++++++++++++++++++++++++++++++----
>  security/landlock/syscalls.c |  2 +-
>  3 files changed, 74 insertions(+), 32 deletions(-)
> 
> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
> index 7d79fc8abe21..e31b97a9f175 100644
> --- a/security/landlock/fs.c
> +++ b/security/landlock/fs.c
> @@ -388,38 +388,22 @@ static bool is_nouser_or_private(const struct dentry *dentry)
>  		unlikely(IS_PRIVATE(d_backing_inode(dentry))));
>  }
>  
> -static access_mask_t
> -get_raw_handled_fs_accesses(const struct landlock_ruleset *const domain)
> -{
> -	access_mask_t access_dom = 0;
> -	size_t layer_level;
> -
> -	for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
> -		access_dom |=
> -			landlock_get_raw_fs_access_mask(domain, layer_level);
> -	return access_dom;
> -}
> -
>  static access_mask_t
>  get_handled_fs_accesses(const struct landlock_ruleset *const domain)
>  {
>  	/* Handles all initially denied by default access rights. */
> -	return get_raw_handled_fs_accesses(domain) |
> +	return landlock_union_access_masks(domain).fs |
>  	       LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
>  }
>  
> -static const struct landlock_ruleset *
> -get_fs_domain(const struct landlock_ruleset *const domain)
> -{
> -	if (!domain || !get_raw_handled_fs_accesses(domain))
> -		return NULL;
> -
> -	return domain;
> -}
> +static const struct access_masks any_fs = {
> +	.fs = ~0,
> +};
>  
>  static const struct landlock_ruleset *get_current_fs_domain(void)
>  {
> -	return get_fs_domain(landlock_get_current_domain());
> +	return landlock_get_applicable_domain(landlock_get_current_domain(),
> +					      any_fs);
>  }
>  
>  /*
> @@ -1517,7 +1501,8 @@ static int hook_file_open(struct file *const file)
>  	access_mask_t open_access_request, full_access_request, allowed_access,
>  		optional_access;
>  	const struct landlock_ruleset *const dom =
> -		get_fs_domain(landlock_cred(file->f_cred)->domain);
> +		landlock_get_applicable_domain(
> +			landlock_cred(file->f_cred)->domain, any_fs);
>  
>  	if (!dom)
>  		return 0;
> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
> index 61bdbc550172..698fa3114cf4 100644
> --- a/security/landlock/ruleset.h
> +++ b/security/landlock/ruleset.h
> @@ -11,6 +11,7 @@
>  
>  #include <linux/bitops.h>
>  #include <linux/build_bug.h>
> +#include <linux/kernel.h>
>  #include <linux/mutex.h>
>  #include <linux/rbtree.h>
>  #include <linux/refcount.h>
> @@ -47,6 +48,15 @@ struct access_masks {
>  	access_mask_t scope : LANDLOCK_NUM_SCOPE;
>  };
>  
> +union access_masks_all {
> +	struct access_masks masks;
> +	u32 all;
> +};
> +
> +/* Makes sure all fields are covered. */
> +static_assert(sizeof(typeof_member(union access_masks_all, masks)) ==
> +	      sizeof(typeof_member(union access_masks_all, all)));
> +
>  typedef u16 layer_mask_t;
>  /* Makes sure all layers can be checked. */
>  static_assert(BITS_PER_TYPE(layer_mask_t) >= LANDLOCK_MAX_NUM_LAYERS);
> @@ -260,6 +270,60 @@ static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
>  		refcount_inc(&ruleset->usage);
>  }
>  
> +/**
> + * landlock_union_access_masks - Return all access rights handled in the
> + *				 domain
> + *
> + * @domain: Landlock ruleset (used as a domain)
> + *
> + * Returns: an access_masks result of the OR of all the domain's access masks.
> + */
> +static inline struct access_masks
> +landlock_union_access_masks(const struct landlock_ruleset *const domain)
> +{
> +	union access_masks_all matches = {};
> +	size_t layer_level;
> +
> +	for (layer_level = 0; layer_level < domain->num_layers; layer_level++) {
> +		union access_masks_all layer = {
> +			.masks = domain->access_masks[layer_level],
> +		};
> +
> +		matches.all |= layer.all;
> +	}
> +
> +	return matches.masks;
> +}
> +
> +/**
> + * landlock_get_applicable_domain - Return @domain if it applies to (handles)
> + *				    the access rights specified in @masks

Very minor wording suggestion: For clarity, I would suggest "at least one of":

  Return @domain if it applies to (handles)
  at least one of the access rights specified in @masks

Otherwise this can be interpreted as "...all of the access rights specified in
@masks".

> + *
> + * @domain: Landlock ruleset (used as a domain)
> + * @masks: access masks
> + *
> + * Returns: @domain if any access rights specified in @masks is handled, or
> + * NULL otherwise.
> + */
> +static inline const struct landlock_ruleset *
> +landlock_get_applicable_domain(const struct landlock_ruleset *const domain,
> +			       const struct access_masks masks)
> +{
> +	const union access_masks_all masks_all = {
> +		.masks = masks,
> +	};
> +	union access_masks_all merge = {};
> +
> +	if (!domain)
> +		return NULL;
> +
> +	merge.masks = landlock_union_access_masks(domain);
> +	if (merge.all & masks_all.all)
> +		return domain;
> +
> +	return NULL;
> +}
> +
>  static inline void
>  landlock_add_fs_access_mask(struct landlock_ruleset *const ruleset,
>  			    const access_mask_t fs_access_mask,
> @@ -295,19 +359,12 @@ landlock_add_scope_mask(struct landlock_ruleset *const ruleset,
>  	ruleset->access_masks[layer_level].scope |= mask;
>  }
>  
> -static inline access_mask_t
> -landlock_get_raw_fs_access_mask(const struct landlock_ruleset *const ruleset,
> -				const u16 layer_level)
> -{
> -	return ruleset->access_masks[layer_level].fs;
> -}
> -
>  static inline access_mask_t
>  landlock_get_fs_access_mask(const struct landlock_ruleset *const ruleset,
>  			    const u16 layer_level)
>  {
>  	/* Handles all initially denied by default access rights. */
> -	return landlock_get_raw_fs_access_mask(ruleset, layer_level) |
> +	return ruleset->access_masks[layer_level].fs |
>  	       LANDLOCK_ACCESS_FS_INITIALLY_DENIED;
>  }
>  
> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> index f5a0e7182ec0..c097d356fa45 100644
> --- a/security/landlock/syscalls.c
> +++ b/security/landlock/syscalls.c
> @@ -329,7 +329,7 @@ static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
>  		return -ENOMSG;
>  
>  	/* Checks that allowed_access matches the @ruleset constraints. */
> -	mask = landlock_get_raw_fs_access_mask(ruleset, 0);
> +	mask = ruleset->access_masks[0].fs;
>  	if ((path_beneath_attr.allowed_access | mask) != mask)
>  		return -EINVAL;
>  
> -- 
> 2.47.0
> 

Reviewed-by: Günther Noack <gnoack@google.com>

Looks good, thanks! Names are much clearer now, IMHO. 👍

—Günther

[PATCH v4 2/3] landlock: Refactor network access mask management

[Mickaël Salaün]

Replace get_raw_handled_net_accesses() and get_current_net_domain() with
a call to landlock_match_ruleset().

Cc: Günther Noack <gnoack@google.com>
Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20241109110856.222842-3-mic@digikod.net
---

Changes since v2:
* Replace get_current_net_domain() with explicit call to
  landlock_match_ruleset().

Changes since v1:
* Rename the all_net mask to any_net.
---
 security/landlock/net.c | 28 ++++++----------------------
 1 file changed, 6 insertions(+), 22 deletions(-)

diff --git a/security/landlock/net.c b/security/landlock/net.c
index c8bcd29bde09..d5dcc4407a19 100644
--- a/security/landlock/net.c
+++ b/security/landlock/net.c
@@ -39,27 +39,9 @@ int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
 	return err;
 }
 
-static access_mask_t
-get_raw_handled_net_accesses(const struct landlock_ruleset *const domain)
-{
-	access_mask_t access_dom = 0;
-	size_t layer_level;
-
-	for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
-		access_dom |= landlock_get_net_access_mask(domain, layer_level);
-	return access_dom;
-}
-
-static const struct landlock_ruleset *get_current_net_domain(void)
-{
-	const struct landlock_ruleset *const dom =
-		landlock_get_current_domain();
-
-	if (!dom || !get_raw_handled_net_accesses(dom))
-		return NULL;
-
-	return dom;
-}
+static const struct access_masks any_net = {
+	.net = ~0,
+};
 
 static int current_check_access_socket(struct socket *const sock,
 				       struct sockaddr *const address,
@@ -72,7 +54,9 @@ static int current_check_access_socket(struct socket *const sock,
 	struct landlock_id id = {
 		.type = LANDLOCK_KEY_NET_PORT,
 	};
-	const struct landlock_ruleset *const dom = get_current_net_domain();
+	const struct landlock_ruleset *const dom =
+		landlock_get_applicable_domain(landlock_get_current_domain(),
+					       any_net);
 
 	if (!dom)
 		return 0;
-- 
2.47.0

Re: [PATCH v4 2/3] landlock: Refactor network access mask management

[Günther Noack]

On Sat, Nov 09, 2024 at 12:08:55PM +0100, Mickaël Salaün wrote:
> Replace get_raw_handled_net_accesses() and get_current_net_domain() with
> a call to landlock_match_ruleset().
> 
> Cc: Günther Noack <gnoack@google.com>
> Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
> Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> Link: https://lore.kernel.org/r/20241109110856.222842-3-mic@digikod.net
> ---
> 
> Changes since v2:
> * Replace get_current_net_domain() with explicit call to
>   landlock_match_ruleset().
> 
> Changes since v1:
> * Rename the all_net mask to any_net.
> ---
>  security/landlock/net.c | 28 ++++++----------------------
>  1 file changed, 6 insertions(+), 22 deletions(-)
> 
> diff --git a/security/landlock/net.c b/security/landlock/net.c
> index c8bcd29bde09..d5dcc4407a19 100644
> --- a/security/landlock/net.c
> +++ b/security/landlock/net.c
> @@ -39,27 +39,9 @@ int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
>  	return err;
>  }
>  
> -static access_mask_t
> -get_raw_handled_net_accesses(const struct landlock_ruleset *const domain)
> -{
> -	access_mask_t access_dom = 0;
> -	size_t layer_level;
> -
> -	for (layer_level = 0; layer_level < domain->num_layers; layer_level++)
> -		access_dom |= landlock_get_net_access_mask(domain, layer_level);
> -	return access_dom;
> -}
> -
> -static const struct landlock_ruleset *get_current_net_domain(void)
> -{
> -	const struct landlock_ruleset *const dom =
> -		landlock_get_current_domain();
> -
> -	if (!dom || !get_raw_handled_net_accesses(dom))
> -		return NULL;
> -
> -	return dom;
> -}
> +static const struct access_masks any_net = {
> +	.net = ~0,
> +};
>  
>  static int current_check_access_socket(struct socket *const sock,
>  				       struct sockaddr *const address,
> @@ -72,7 +54,9 @@ static int current_check_access_socket(struct socket *const sock,
>  	struct landlock_id id = {
>  		.type = LANDLOCK_KEY_NET_PORT,
>  	};
> -	const struct landlock_ruleset *const dom = get_current_net_domain();
> +	const struct landlock_ruleset *const dom =
> +		landlock_get_applicable_domain(landlock_get_current_domain(),
> +					       any_net);
>  
>  	if (!dom)
>  		return 0;
> -- 
> 2.47.0
> 

Reviewed-by: Günther Noack <gnoack@google.com>

—Günther

[PATCH v4 3/3] landlock: Optimize scope enforcement

[Mickaël Salaün]

Do not walk through the domain hierarchy when the required scope is not
supported by this domain.  This is the same approach as for filesystem
and network restrictions.

Cc: Günther Noack <gnoack@google.com>
Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
Cc: Tahera Fahimi <fahimitahera@gmail.com>
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Link: https://lore.kernel.org/r/20241109110856.222842-4-mic@digikod.net
---

Changes since v2:
* Make the unix_scope variable global to the file and remove
  previous get_current_unix_scope_domain().
---
 security/landlock/task.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/security/landlock/task.c b/security/landlock/task.c
index 4acbd7c40eee..dc7dab78392e 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -204,12 +204,17 @@ static bool is_abstract_socket(struct sock *const sock)
 	return false;
 }
 
+static const struct access_masks unix_scope = {
+	.scope = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET,
+};
+
 static int hook_unix_stream_connect(struct sock *const sock,
 				    struct sock *const other,
 				    struct sock *const newsk)
 {
 	const struct landlock_ruleset *const dom =
-		landlock_get_current_domain();
+		landlock_get_applicable_domain(landlock_get_current_domain(),
+					       unix_scope);
 
 	/* Quick return for non-landlocked tasks. */
 	if (!dom)
@@ -225,7 +230,8 @@ static int hook_unix_may_send(struct socket *const sock,
 			      struct socket *const other)
 {
 	const struct landlock_ruleset *const dom =
-		landlock_get_current_domain();
+		landlock_get_applicable_domain(landlock_get_current_domain(),
+					       unix_scope);
 
 	if (!dom)
 		return 0;
@@ -243,6 +249,10 @@ static int hook_unix_may_send(struct socket *const sock,
 	return 0;
 }
 
+static const struct access_masks signal_scope = {
+	.scope = LANDLOCK_SCOPE_SIGNAL,
+};
+
 static int hook_task_kill(struct task_struct *const p,
 			  struct kernel_siginfo *const info, const int sig,
 			  const struct cred *const cred)
@@ -256,6 +266,7 @@ static int hook_task_kill(struct task_struct *const p,
 	} else {
 		dom = landlock_get_current_domain();
 	}
+	dom = landlock_get_applicable_domain(dom, signal_scope);
 
 	/* Quick return for non-landlocked tasks. */
 	if (!dom)
@@ -279,7 +290,8 @@ static int hook_file_send_sigiotask(struct task_struct *tsk,
 
 	/* Lock already held by send_sigio() and send_sigurg(). */
 	lockdep_assert_held(&fown->lock);
-	dom = landlock_file(fown->file)->fown_domain;
+	dom = landlock_get_applicable_domain(
+		landlock_file(fown->file)->fown_domain, signal_scope);
 
 	/* Quick return for unowned socket. */
 	if (!dom)
-- 
2.47.0

Re: [PATCH v4 3/3] landlock: Optimize scope enforcement

[Günther Noack]

On Sat, Nov 09, 2024 at 12:08:56PM +0100, Mickaël Salaün wrote:
> Do not walk through the domain hierarchy when the required scope is not
> supported by this domain.  This is the same approach as for filesystem
> and network restrictions.
> 
> Cc: Günther Noack <gnoack@google.com>
> Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
> Cc: Tahera Fahimi <fahimitahera@gmail.com>
> Signed-off-by: Mickaël Salaün <mic@digikod.net>
> Link: https://lore.kernel.org/r/20241109110856.222842-4-mic@digikod.net
> ---
> 
> Changes since v2:
> * Make the unix_scope variable global to the file and remove
>   previous get_current_unix_scope_domain().
> ---
>  security/landlock/task.c | 18 +++++++++++++++---
>  1 file changed, 15 insertions(+), 3 deletions(-)
> 
> diff --git a/security/landlock/task.c b/security/landlock/task.c
> index 4acbd7c40eee..dc7dab78392e 100644
> --- a/security/landlock/task.c
> +++ b/security/landlock/task.c
> @@ -204,12 +204,17 @@ static bool is_abstract_socket(struct sock *const sock)
>  	return false;
>  }
>  
> +static const struct access_masks unix_scope = {
> +	.scope = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET,
> +};

Optional nit: You could probably inline these two struct access_masks values
into the respective functions where they are used.  (But it's just a minor code
style matter IMHO; both ways are fine.)

> +
>  static int hook_unix_stream_connect(struct sock *const sock,
>  				    struct sock *const other,
>  				    struct sock *const newsk)
>  {
>  	const struct landlock_ruleset *const dom =
> -		landlock_get_current_domain();
> +		landlock_get_applicable_domain(landlock_get_current_domain(),
> +					       unix_scope);
>  
>  	/* Quick return for non-landlocked tasks. */
>  	if (!dom)
> @@ -225,7 +230,8 @@ static int hook_unix_may_send(struct socket *const sock,
>  			      struct socket *const other)
>  {
>  	const struct landlock_ruleset *const dom =
> -		landlock_get_current_domain();
> +		landlock_get_applicable_domain(landlock_get_current_domain(),
> +					       unix_scope);
>  
>  	if (!dom)
>  		return 0;
> @@ -243,6 +249,10 @@ static int hook_unix_may_send(struct socket *const sock,
>  	return 0;
>  }
>  
> +static const struct access_masks signal_scope = {
> +	.scope = LANDLOCK_SCOPE_SIGNAL,
> +};
> +
>  static int hook_task_kill(struct task_struct *const p,
>  			  struct kernel_siginfo *const info, const int sig,
>  			  const struct cred *const cred)
> @@ -256,6 +266,7 @@ static int hook_task_kill(struct task_struct *const p,
>  	} else {
>  		dom = landlock_get_current_domain();
>  	}
> +	dom = landlock_get_applicable_domain(dom, signal_scope);
>  
>  	/* Quick return for non-landlocked tasks. */
>  	if (!dom)
> @@ -279,7 +290,8 @@ static int hook_file_send_sigiotask(struct task_struct *tsk,
>  
>  	/* Lock already held by send_sigio() and send_sigurg(). */
>  	lockdep_assert_held(&fown->lock);
> -	dom = landlock_file(fown->file)->fown_domain;
> +	dom = landlock_get_applicable_domain(
> +		landlock_file(fown->file)->fown_domain, signal_scope);
>  
>  	/* Quick return for unowned socket. */
>  	if (!dom)
> -- 
> 2.47.0
> 

Reviewed-by: Günther Noack <gnoack@google.com>

Looks good!

—Günther

Re: [PATCH v4 3/3] landlock: Optimize scope enforcement

[Mickaël Salaün]

On Sat, Nov 09, 2024 at 07:30:28PM +0100, Günther Noack wrote:
> On Sat, Nov 09, 2024 at 12:08:56PM +0100, Mickaël Salaün wrote:
> > Do not walk through the domain hierarchy when the required scope is not
> > supported by this domain.  This is the same approach as for filesystem
> > and network restrictions.
> > 
> > Cc: Günther Noack <gnoack@google.com>
> > Cc: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
> > Cc: Tahera Fahimi <fahimitahera@gmail.com>
> > Signed-off-by: Mickaël Salaün <mic@digikod.net>
> > Link: https://lore.kernel.org/r/20241109110856.222842-4-mic@digikod.net
> > ---
> > 
> > Changes since v2:
> > * Make the unix_scope variable global to the file and remove
> >   previous get_current_unix_scope_domain().
> > ---
> >  security/landlock/task.c | 18 +++++++++++++++---
> >  1 file changed, 15 insertions(+), 3 deletions(-)
> > 
> > diff --git a/security/landlock/task.c b/security/landlock/task.c
> > index 4acbd7c40eee..dc7dab78392e 100644
> > --- a/security/landlock/task.c
> > +++ b/security/landlock/task.c
> > @@ -204,12 +204,17 @@ static bool is_abstract_socket(struct sock *const sock)
> >  	return false;
> >  }
> >  
> > +static const struct access_masks unix_scope = {
> > +	.scope = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET,
> > +};
> 
> Optional nit: You could probably inline these two struct access_masks values
> into the respective functions where they are used.  (But it's just a minor code
> style matter IMHO; both ways are fine.)

That was the case in a previous version, but because we'll need to have
it global for a next patch series, I already put it there to avoid
useless code change:
https://lore.kernel.org/all/20241022161009.982584-14-mic@digikod.net/

> 
> > +
> >  static int hook_unix_stream_connect(struct sock *const sock,
> >  				    struct sock *const other,
> >  				    struct sock *const newsk)
> >  {
> >  	const struct landlock_ruleset *const dom =
> > -		landlock_get_current_domain();
> > +		landlock_get_applicable_domain(landlock_get_current_domain(),
> > +					       unix_scope);
> >  
> >  	/* Quick return for non-landlocked tasks. */
> >  	if (!dom)
> > @@ -225,7 +230,8 @@ static int hook_unix_may_send(struct socket *const sock,
> >  			      struct socket *const other)
> >  {
> >  	const struct landlock_ruleset *const dom =
> > -		landlock_get_current_domain();
> > +		landlock_get_applicable_domain(landlock_get_current_domain(),
> > +					       unix_scope);
> >  
> >  	if (!dom)
> >  		return 0;
> > @@ -243,6 +249,10 @@ static int hook_unix_may_send(struct socket *const sock,
> >  	return 0;
> >  }
> >  
> > +static const struct access_masks signal_scope = {
> > +	.scope = LANDLOCK_SCOPE_SIGNAL,
> > +};
> > +
> >  static int hook_task_kill(struct task_struct *const p,
> >  			  struct kernel_siginfo *const info, const int sig,
> >  			  const struct cred *const cred)
> > @@ -256,6 +266,7 @@ static int hook_task_kill(struct task_struct *const p,
> >  	} else {
> >  		dom = landlock_get_current_domain();
> >  	}
> > +	dom = landlock_get_applicable_domain(dom, signal_scope);
> >  
> >  	/* Quick return for non-landlocked tasks. */
> >  	if (!dom)
> > @@ -279,7 +290,8 @@ static int hook_file_send_sigiotask(struct task_struct *tsk,
> >  
> >  	/* Lock already held by send_sigio() and send_sigurg(). */
> >  	lockdep_assert_held(&fown->lock);
> > -	dom = landlock_file(fown->file)->fown_domain;
> > +	dom = landlock_get_applicable_domain(
> > +		landlock_file(fown->file)->fown_domain, signal_scope);
> >  
> >  	/* Quick return for unowned socket. */
> >  	if (!dom)
> > -- 
> > 2.47.0
> > 
> 
> Reviewed-by: Günther Noack <gnoack@google.com>
> 
> Looks good!

Thanks!

> 
> —Günther
>