linux-kernel - Re: [PATCH v1 2/2] io_uring,audit: do not log IORING_OP

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Date:   Fri, 27 Jan 2023 19:07:17 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Richard Guy Briggs <rgb@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>, io-uring@...r.kernel.org,
        Eric Paris <eparis@...isplace.org>,
        Steve Grubb <sgrubb@...hat.com>, Stefan Roesch <shr@...com>,
        Christian Brauner <brauner@...nel.org>,
        Pavel Begunkov <asml.silence@...il.com>
Subject: Re: [PATCH v1 2/2] io_uring,audit: do not log IORING_OP_*GETXATTR

On Fri, Jan 27, 2023 at 6:05 PM Jens Axboe <axboe@...nel.dk> wrote:
> On 1/27/23 4:01 PM, Richard Guy Briggs wrote:
> > On 2023-01-27 17:43, Paul Moore wrote:
> >> On Fri, Jan 27, 2023 at 12:24 PM Richard Guy Briggs <rgb@...hat.com> wrote:
> >>> Getting XATTRs is not particularly interesting security-wise.
> >>>
> >>> Suggested-by: Steve Grubb <sgrubb@...hat.com>
> >>> Fixes: a56834e0fafe ("io_uring: add fgetxattr and getxattr support")
> >>> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> >>> ---
> >>>  io_uring/opdef.c | 2 ++
> >>>  1 file changed, 2 insertions(+)
> >>
> >> Depending on your security policy, fetching file data, including
> >> xattrs, can be interesting from a security perspective.  As an
> >> example, look at the SELinux file/getattr permission.
> >>
> >> https://github.com/SELinuxProject/selinux-notebook/blob/main/src/object_classes_permissions.md#common-file-permissions
> >
> > The intent here is to lessen the impact of audit operations.  Read and
> > Write were explicitly removed from io_uring auditing due to performance
> > concerns coupled with the denial of service implications from sheer
> > volume of records making other messages harder to locate.  Those
> > operations are still possible for syscall auditing but they are strongly
> > discouraged for normal use.
> >
> > If the frequency of getxattr io_uring ops is so infrequent as to be no
> > distraction, then this patch may be more of a liability than a benefit.
>
> (audit list removed)
>
> Right now the xattr related functions are io-wq driven, and hence not
> super performance sensitive. But I'd greatly prefer to clean these up
> regardless, because once opcodes get upgraded from needing io-wq, then
> we don't have to go through the audit discussion at that point. Better
> to do it upfront, like now, regardless of expectation of frequency of
> calls.

See my reply to Richard, but unfortunately we need to continue to
audit the getxattr ops.

-- 
paul-moore.com