On Tue, Aug 16, 2022 at 09:18:33PM +0200, Mickaël Salaün wrote:

On 14/08/2022 21:26, Günther Noack wrote:

quoted

diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst
index 6648e59fabe7..3ceb97cbe9d1 100644
--- a/Documentation/userspace-api/landlock.rst
+++ b/Documentation/userspace-api/landlock.rst
  Because we may not know on which kernel version an application will be

@@ -69,16 +70,26 @@ should try to protect users as much as possible whatever the kernel they are
  using.  To avoid binary enforcement (i.e. either all security features or
  none), we can leverage a dedicated Landlock command to get the current version
  of the Landlock ABI and adapt the handled accesses.  Let's check if we should
-remove the `LANDLOCK_ACCESS_FS_REFER` access right which is only supported
-starting with the second version of the ABI.
+remove the `LANDLOCK_ACCESS_FS_REFER` and `LANDLOCK_ACCESS_FS_TRUNCATE` access

s/and/or/

Done.

quoted

+Truncating files
+----------------
+
+The operations covered by `LANDLOCK_ACCESS_FS_WRITE_FILE` and
+`LANDLOCK_ACCESS_FS_TRUNCATE` both change the contents of a file and sometimes
+overlap in non-intuitive ways.  It is recommended to always specify both of
+these together.
+
+A particularly surprising example is :manpage:`creat(2)`.  The name suggests
+that this system call requires the rights to create and write files.  However,
+it also requires the truncate right if an existing file under the same name is
+already present.
+
+It should also be noted that truncating files does not necessarily require the

I think "necessarily" is superfluous here.

Done.  I dropped the "obvious" too.

quoted

+`LANDLOCK_ACCESS_FS_WRITE_FILE` right.  Apart from the obvious
+:manpage:`truncate(2)` system call, this can also be done through
+:manpage:`open(2)` with the flags `O_RDONLY` and `O_TRUNC`.

`O_RDONLY | O_TRUNC`.

Done.

quoted

  Compatibility
  =============

@@ -386,9 +415,8 @@ File truncation (ABI < 3)
  File truncation could not be denied before the third Landlock ABI, so it is
  always allowed when using a kernel that only supports the first or second ABI.
-Starting with the Landlock ABI version 3, it is now possible to securely
-control truncation thanks to the new `LANDLOCK_ACCESS_FS_TRUNCATE` access
-right.
+Starting with the Landlock ABI version 3, it is now possible to securely control
+truncation thanks to the new `LANDLOCK_ACCESS_FS_TRUNCATE` access right.

This is an inconsistent hunk, patching the first patch.

Please also move this "File truncation" section below the "File renaming and
linking".

Thanks, fixed the ordering of commits and moved the truncation section
below "File Renaming and Linking".

—Günther

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