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

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Date:   Fri, 27 Jan 2023 18:08:03 -0500
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>
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 2023-01-27 16:03, Jens Axboe wrote:
> 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?

Gladly.

> Jens Axboe

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635