On Thu, Mar 17, 2022 at 4:35 AM Mickaël Salaün [off-list ref] wrote:

On 17/03/2022 02:26, Paul Moore wrote:

quoted

On Mon, Feb 21, 2022 at 4:15 PM Mickaël Salaün [off-list ref] wrote:

quoted

From: Mickaël Salaün <redacted>

Create and use the access_mask_t typedef to enforce a consistent access
mask size and uniformly use a 16-bits type.  This will helps transition
to a 32-bits value one day.

Add a build check to make sure all (filesystem) access rights fit in.
This will be extended with a following commit.

Signed-off-by: Mickaël Salaün <redacted>
Link: https://lore.kernel.org/r/20220221212522.320243-2-mic@digikod.net (local)
---
  security/landlock/fs.c      | 19 ++++++++++---------
  security/landlock/fs.h      |  2 +-
  security/landlock/limits.h  |  2 ++
  security/landlock/ruleset.c |  6 ++++--
  security/landlock/ruleset.h | 17 +++++++++++++----
  5 files changed, 30 insertions(+), 16 deletions(-)

...

quoted

quoted

diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index 2a0a1095ee27..458d1de32ed5 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h

@@ -9,6 +9,7 @@
  #ifndef _SECURITY_LANDLOCK_LIMITS_H
  #define _SECURITY_LANDLOCK_LIMITS_H

+#include <linux/bitops.h>
  #include <linux/limits.h>
  #include <uapi/linux/landlock.h>

@@ -17,5 +18,6 @@

  #define LANDLOCK_LAST_ACCESS_FS                LANDLOCK_ACCESS_FS_MAKE_SYM
  #define LANDLOCK_MASK_ACCESS_FS                ((LANDLOCK_LAST_ACCESS_FS << 1) - 1)
+#define LANDLOCK_NUM_ACCESS_FS         __const_hweight64(LANDLOCK_MASK_ACCESS_FS)

The line above, and the static_assert() in ruleset.h are clever.  I'll
admit I didn't even know the hweightX() macros existed until looking
at this code :)

However, the LANDLOCK_NUM_ACCESS_FS is never really going to be used
outside the static_assert() in ruleset.h is it?  I wonder if it would
be better to skip the extra macro and rewrite the static_assert like
this:

static_assert(BITS_PER_TYPE(access_mask_t) >=
__const_hweight64(LANDLOCK_MASK_ACCESS_FS));

If not, I might suggest changing LANDLOCK_NUM_ACCESS_FS to
LANDLOCK_BITS_ACCESS_FS or something similar.

I declared LANDLOCK_NUM_ACCESS_FS in this patch to be able to have the
static_assert() here and ease the review, but LANDLOCK_NUM_ACCESS_FS is
really used in patch 6/11 to define an array size:
get_handled_acceses(), init_layer_masks(), is_superset(),
check_access_path_dual()…

I wrote my comments as I was working my way through the patchset and
didn't think to go back and check this when I hit patch 6/11 :)

Looks good to me, sorry for the noise.

Reviewed-by: Paul Moore <paul@paul-moore.com>

-- 
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