Re: [PATCH v1 05/11] landlock: Move filesystem helpers and add a new one

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On 17/03/2022 02:26, Paul Moore wrote:
On Mon, Feb 21, 2022 at 4:15 PM Mickaël Salaün <mic@xxxxxxxxxxx> wrote:

From: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx>

Move the SB_NOUSER and IS_PRIVATE dentry check to a standalone
is_nouser_or_private() helper.  This will be useful for a following
commit.

Move get_mode_access() and maybe_remove() to make them usable by new
code provided by a following commit.

Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20220221212522.320243-6-mic@xxxxxxxxxxx
---
  security/landlock/fs.c | 87 ++++++++++++++++++++++--------------------
  1 file changed, 46 insertions(+), 41 deletions(-)

One nit-picky comment below, otherwise it looks fine to me.

Reviewed-by: Paul Moore <paul@xxxxxxxxxxxxxx>

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 9662f9fb3cd0..3886f9ad1a60 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -257,6 +257,18 @@ static inline bool unmask_layers(const struct landlock_rule *const rule,
         return false;
  }

+static inline bool is_nouser_or_private(const struct dentry *dentry)
+{
+       /*
+        * Allows access to pseudo filesystems that will never be mountable
+        * (e.g. sockfs, pipefs), but can still be reachable through
+        * /proc/<pid>/fd/<file-descriptor> .
+        */

I might suggest moving this explanation up to a function header comment block.

Sounds good.




+       return (dentry->d_sb->s_flags & SB_NOUSER) ||
+                       (d_is_positive(dentry) &&
+                        unlikely(IS_PRIVATE(d_backing_inode(dentry))));
+}
+
  static int check_access_path(const struct landlock_ruleset *const domain,
                 const struct path *const path,
                 const access_mask_t access_request)

--
paul-moore.com



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