On 17/03/2022 14:25, Konstantin Meskhidze wrote:

3/15/2022 8:48 PM, Mickaël Salaün пишет:

…

quoted

quoted

diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index 78341a0538de..a6212b752549 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c

@@ -44,16 +44,30 @@ static struct landlock_ruleset 

*create_ruleset(const u32 num_layers)
      return new_ruleset;
  }

-struct landlock_ruleset *landlock_create_ruleset(const u32 access_mask)
+/* A helper function to set a filesystem mask */
+void landlock_set_fs_access_mask(struct landlock_ruleset *ruleset,

struct landlock_ruleset *const ruleset

Please use const as much as possible even in function arguments: e.g. 
access_masks_set, mask_level…

quoted

+                 const struct landlock_access_mask *access_mask_set,

  Ok. Got it.

quoted

nit: no need for "_set" suffix.

  Ok. Thanks

quoted

Why do you need a struct landlock_access_mask and not just u16 (which 
will probably become a subset of access_mask_t, see [1])? 
landlock_create_ruleset() could just take two masks as argument instead.

[1] https://lore.kernel.org/all/20220221212522.320243-2-mic@digikod.net/ (local)

   This was your suggestion in previous patch V3:

   " To make it easier and avoid mistakes, you could use a dedicated
    struct to properly manage masks passing and conversions:
   struct landlock_access_mask {
     u16 fs; // TODO: make sure at build-time that all access rights
                    fit in.
     u16 net; // TODO: ditto for network access rights.
   }

   get_access_masks(const struct landlock_ruleset *, struct
   landlock_access_mask *);
   set_access_masks(struct landlock_ruleset *, const struct
   landlock_access_mask *);

   This should also be part of a standalone patch."


https://lore.kernel.org/linux-security-module/ed2bd420-a22b-2912-1ff5-f48ab352d8e7@digikod.net/ (local) 

Indeed! What is nice about struct is that it enables to easily 
differentiate same-type values (e.g. fs mask from net mask). However, 
because this struct is mainly passed once to initialize a ruleset, it 
looks like this was not worth it. Please get back to how you dealt with 
that previously but with a new access_mask_t typedef, which will 
conflict with my latest patchset but that will be trivial to fix. You 
can also merge the landlock_set_*_access_mask() into 
landlock_create_ruleset() because they are not use elsewhere (and then 
it would have been much less useful to have a dedicated struct).

quoted

quoted

+                 u16 mask_level)
+{
+    ruleset->access_masks[mask_level] = access_mask_set->fs;
+}
+
+/* A helper function to get a filesystem mask */
+u32 landlock_get_fs_access_mask(const struct landlock_ruleset 
*ruleset, u16 mask_level)
+{
+    return ruleset->access_masks[mask_level];
+}

You can move these two helpers to ruleset.h and make them static inline.

   Ok. I got it.

quoted

quoted

+
+struct landlock_ruleset *landlock_create_ruleset(const struct 
landlock_access_mask *access_mask_set)
  {
      struct landlock_ruleset *new_ruleset;

      /* Informs about useless ruleset. */
-    if (!access_mask)
+    if (!access_mask_set->fs)
          return ERR_PTR(-ENOMSG);
      new_ruleset = create_ruleset(1);
      if (!IS_ERR(new_ruleset))
-        new_ruleset->access_masks[0] = access_mask;
+        landlock_set_fs_access_mask(new_ruleset, access_mask_set, 0);
      return new_ruleset;
  }

diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
index 32d90ce72428..bc87e5f787f7 100644
--- a/security/landlock/ruleset.h
+++ b/security/landlock/ruleset.h

@@ -16,6 +16,16 @@

  #include "object.h"

+/**
+ * struct landlock_access_mask - A helper structure to handle 
different mask types
+ */
+struct landlock_access_mask {
+    /**
+     * @fs: Filesystem access mask.
+     */
+    u16 fs;
+};

Removing this struct would simplify the code.

   I followed your recommendation to use such kind of structure.
   Please check previous patch V3 review:


https://lore.kernel.org/linux-security-module/ed2bd420-a22b-2912-1ff5-f48ab352d8e7@digikod.net/ (local) 

quoted

quoted

+
  /**
   * struct landlock_layer - Access rights for a given layer
   */

@@ -140,7 +150,8 @@ struct landlock_ruleset {

      };
  };

-struct landlock_ruleset *landlock_create_ruleset(const u32 
access_mask);
+struct landlock_ruleset *landlock_create_ruleset(const struct 
landlock_access_mask
+                                    *access_mask_set);

  void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
  void landlock_put_ruleset_deferred(struct landlock_ruleset *const 
ruleset);

@@ -162,4 +173,10 @@ static inline void landlock_get_ruleset(struct 

landlock_ruleset *const ruleset)
          refcount_inc(&ruleset->usage);
  }

+void landlock_set_fs_access_mask(struct landlock_ruleset *ruleset,
+                 const struct landlock_access_mask *access_mask_set,
+                 u16 mask_level);
+
+u32 landlock_get_fs_access_mask(const struct landlock_ruleset 
*ruleset, u16 mask_level);
+
  #endif /* _SECURITY_LANDLOCK_RULESET_H */

diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index f1d86311df7e..5931b666321d 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c

@@ -159,6 +159,7 @@ SYSCALL_DEFINE3(landlock_create_ruleset,

  {
      struct landlock_ruleset_attr ruleset_attr;
      struct landlock_ruleset *ruleset;
+    struct landlock_access_mask access_mask_set = {.fs = 0};
      int err, ruleset_fd;

      /* Build-time checks. */

@@ -185,9 +186,10 @@ SYSCALL_DEFINE3(landlock_create_ruleset,

      if ((ruleset_attr.handled_access_fs | LANDLOCK_MASK_ACCESS_FS) !=
              LANDLOCK_MASK_ACCESS_FS)
          return -EINVAL;
+    access_mask_set.fs = ruleset_attr.handled_access_fs;

      /* Checks arguments and transforms to kernel struct. */
-    ruleset = landlock_create_ruleset(ruleset_attr.handled_access_fs);
+    ruleset = landlock_create_ruleset(&access_mask_set);
      if (IS_ERR(ruleset))
          return PTR_ERR(ruleset);

@@ -343,8 +345,9 @@ SYSCALL_DEFINE4(landlock_add_rule,

       * Checks that allowed_access matches the @ruleset constraints
       * (ruleset->access_masks[0] is automatically upgraded to 
64-bits).
       */
-    if ((path_beneath_attr.allowed_access | 
ruleset->access_masks[0]) !=
-            ruleset->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

.