Re: [PATCH] Smack: Provide read control for io_uring_cmd

[Paul Moore <paul@paul-moore.com>]

On Fri, Aug 26, 2022 at 12:53 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> On 8/26/2022 8:15 AM, Paul Moore wrote:
> > On Tue, Aug 23, 2022 at 8:07 PM Jens Axboe <axboe@kernel.dk> wrote:
> >> On 8/23/22 6:05 PM, Paul Moore wrote:
> >>> On Tue, Aug 23, 2022 at 7:46 PM Casey Schaufler <casey@schaufler-ca.com> wrote:
> >>>> Limit io_uring "cmd" options to files for which the caller has
> >>>> Smack read access. There may be cases where the cmd option may
> >>>> be closer to a write access than a read, but there is no way
> >>>> to make that determination.
> >>>>
> >>>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> >>>> --
> >>>>  security/smack/smack_lsm.c | 32 ++++++++++++++++++++++++++++++++
> >>>>  1 file changed, 32 insertions(+)
> >>>>
> >>>> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> >>>> index 001831458fa2..bffccdc494cb 100644
> >>>> --- a/security/smack/smack_lsm.c
> >>>> +++ b/security/smack/smack_lsm.c
> >>> ...
> >>>
> >>>> @@ -4732,6 +4733,36 @@ static int smack_uring_sqpoll(void)
> >>>>         return -EPERM;
> >>>>  }
> >>>>
> >>>> +/**
> >>>> + * smack_uring_cmd - check on file operations for io_uring
> >>>> + * @ioucmd: the command in question
> >>>> + *
> >>>> + * Make a best guess about whether a io_uring "command" should
> >>>> + * be allowed. Use the same logic used for determining if the
> >>>> + * file could be opened for read in the absence of better criteria.
> >>>> + */
> >>>> +static int smack_uring_cmd(struct io_uring_cmd *ioucmd)
> >>>> +{
> >>>> +       struct file *file = ioucmd->file;
> >>>> +       struct smk_audit_info ad;
> >>>> +       struct task_smack *tsp;
> >>>> +       struct inode *inode;
> >>>> +       int rc;
> >>>> +
> >>>> +       if (!file)
> >>>> +               return -EINVAL;
> >>> Perhaps this is a better question for Jens, but ioucmd->file is always
> >>> going to be valid when the LSM hook is called, yes?
> >> file will always be valid for uring commands, as they are marked as
> >> requiring a file. If no valid fd is given for it, it would've been
> >> errored early on, before reaching f_op->uring_cmd().
> > Hey Casey, where do things stand with this patch?  To be specific, did
> > you want me to include this in the lsm/stable-6.0 PR for Linus or are
> > you planning to send it separately?  If you want me to send it up, are
> > you planning another revision?
> >
> > There is no right or wrong answer here as far as I'm concerned, I'm
> > just trying to make sure we are all on the same page.
>
> I think the whole LSM fix for io_uring looks better the more complete
> it is. I don't see the Smack check changing until such time as there's
> better information available to make decisions upon. If you send it along
> with the rest of the patch set I think we'll have done our best.

Okay, will do.  Would you like me to tag the patch with the 'Fixes:'
and stable tags, similar to the LSM and SELinux patches?

-- 
paul-moore.com