On Fri, Jul 29, 2022 at 12:47:46PM +0200, Mickaël Salaün wrote: > > On 12/07/2022 23:14, Günther Noack wrote: > > Use the LANDLOCK_ACCESS_FS_TRUNCATE flag in the tutorial. > > > > Adapt the backwards compatibility example and discussion to remove the > > truncation flag if needed. > > > > Signed-off-by: Günther Noack <gnoack3000@xxxxxxxxx> > > Link: https://lore.kernel.org/all/20220707200612.132705-1-gnoack3000@xxxxxxxxx/ > > --- > > Documentation/userspace-api/landlock.rst | 19 ++++++++++++++----- > > 1 file changed, 14 insertions(+), 5 deletions(-) > > > > diff --git a/Documentation/userspace-api/landlock.rst b/Documentation/userspace-api/landlock.rst > > index b86fd94ae797..41fa464cc8b8 100644 > > --- a/Documentation/userspace-api/landlock.rst > > +++ b/Documentation/userspace-api/landlock.rst > > @@ -60,7 +60,8 @@ the need to be explicit about the denied-by-default access rights. > > LANDLOCK_ACCESS_FS_MAKE_FIFO | > > LANDLOCK_ACCESS_FS_MAKE_BLOCK | > > LANDLOCK_ACCESS_FS_MAKE_SYM | > > - LANDLOCK_ACCESS_FS_REFER, > > + LANDLOCK_ACCESS_FS_REFER | > > + LANDLOCK_ACCESS_FS_TRUNCATE, > > }; > > Because we may not know on which kernel version an application will be > > @@ -69,14 +70,22 @@ 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 > > +rights, which are only supported starting with the second and third version of > > +the ABI. > > .. code-block:: c > > int abi; > > abi = landlock_create_ruleset(NULL, 0, LANDLOCK_CREATE_RULESET_VERSION); > > + if (abi == -1) { > > + perror("Landlock is unsupported on this kernel"); > > "Landlock is not supported with the running kernel"? Done. > > > > + return 1; > > + } > > + if (abi < 3) { > > + ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_TRUNCATE; > > + } > > I guess we could use the same switch/case code as for the sample. I'm not > sure what would be the less confusing for users though. Done. (Both are mildly confusing, IMHO %-)) > [...] --
