linux-kernel - Re: [PATCH v1 1/2] io_uring,audit: audit IORING_OP_FADVISE but not IORING_OP

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Message-ID: <68b599bb-2329-3125-1859-cf529fbeea00@kernel.dk>
Date:   Fri, 27 Jan 2023 16:03:45 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     Paul Moore <paul@...l-moore.com>,
        Linux-Audit Mailing List <linux-audit@...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 1/2] io_uring,audit: audit IORING_OP_FADVISE but not
 IORING_OP_MADVISE

On 1/27/23 4:02 PM, Richard Guy Briggs wrote:
> On 2023-01-27 15:45, Jens Axboe wrote:
>> On 1/27/23 3:35?PM, Paul Moore wrote:
>>> On Fri, Jan 27, 2023 at 12:24 PM Richard Guy Briggs <rgb@...hat.com> wrote:
>>>>
>>>> Since FADVISE can truncate files and MADVISE operates on memory, reverse
>>>> the audit_skip tags.
>>>>
>>>> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
>>>> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
>>>> ---
>>>>  io_uring/opdef.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/io_uring/opdef.c b/io_uring/opdef.c
>>>> index 3aa0d65c50e3..a2bf53b4a38a 100644
>>>> --- a/io_uring/opdef.c
>>>> +++ b/io_uring/opdef.c
>>>> @@ -306,12 +306,12 @@ const struct io_op_def io_op_defs[] = {
>>>>         },
>>>>         [IORING_OP_FADVISE] = {
>>>>                 .needs_file             = 1,
>>>> -               .audit_skip             = 1,
>>>>                 .name                   = "FADVISE",
>>>>                 .prep                   = io_fadvise_prep,
>>>>                 .issue                  = io_fadvise,
>>>>         },
>>>
>>> I've never used posix_fadvise() or the associated fadvise64*()
>>> syscalls, but from quickly reading the manpages and the
>>> generic_fadvise() function in the kernel I'm missing where the fadvise
>>> family of functions could be used to truncate a file, can you show me
>>> where this happens?  The closest I can see is the manipulation of the
>>> page cache, but that shouldn't actually modify the file ... right?
>>
>> Yeah, honestly not sure where that came from. Maybe it's being mixed up
>> with fallocate? All fadvise (or madvise, for that matter) does is
>> provide hints on the caching or access pattern. On second thought, both
>> of these should be able to set audit_skip as far as I can tell.
> 
> That was one suspicion I had.  If this is the case, I'd agree both could
> be skipped.

I'd be surprised if Steve didn't mix them up. Once he responds, can you
send a v2 with the correction?

-- 
Jens Axboe