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

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Message-ID: <5270af37-5544-42de-4e3f-c437889944dd@kernel.dk>
Date:   Fri, 27 Jan 2023 16:05:29 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Richard Guy Briggs <rgb@...hat.com>,
        Paul Moore <paul@...l-moore.com>
Cc:     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 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.

-- 
Jens Axboe