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Subject: Re: Regression in 5.1.20: Reading long directory fails
From:   Chuck Lever <chuck.lever@oracle.com>
In-Reply-To: <8D7EFCEB-4AE6-4963-B66F-4A8EEA5EA42A@redhat.com>
Date:   Wed, 11 Sep 2019 13:43:37 -0400
Cc:     Jason L Tibbitts III <tibbs@math.uh.edu>,
        Bruce Fields <bfields@fieldses.org>,
        Wolfgang Walter <linux@stwm.de>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        km@cm4all.com, linux-kernel@vger.kernel.org
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To:     Benjamin Coddington <bcodding@redhat.com>
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> On Sep 11, 2019, at 1:40 PM, Benjamin Coddington <bcodding@redhat.com> =
wrote:
>=20
> On 11 Sep 2019, at 13:29, Chuck Lever wrote:
>=20
>>> On Sep 11, 2019, at 1:26 PM, Benjamin Coddington =
<bcodding@redhat.com> wrote:
>>>=20
>>>=20
>>> On 11 Sep 2019, at 12:39, Chuck Lever wrote:
>>>=20
>>>>> On Sep 11, 2019, at 12:25 PM, Benjamin Coddington =
<bcodding@redhat.com> wrote:
>>>>>=20
>>>=20
>>>>> Instead, I think we want to make sure the mic falls squarely into =
the tail
>>>>> every time.
>>>>=20
>>>> I'm not clear how you could do that. The length of the page data is =
not
>>>> known to the client before it parses the reply. Are you suggesting =
that
>>>> gss_unwrap should do it somehow?
>>>=20
>>> Is it too niave to always put the mic at the end of the tail?
>>=20
>> The size of the page content is variable.
>>=20
>> The only way the MIC will fall into the tail is if the page content =
is
>> exactly the largest expected size. When the page content is smaller =
than
>> that, the receive logic will place part or all of the MIC in ->pages.
>=20
> Ok, right.  But what I meant is that xdr_buf_read_netobj() should be =
renamed
> and repurposed to be "move the mic from wherever it is to the end of
> xdr_buf's tail".
>=20
> But now I see what you mean, and I also see that it is already trying =
to do
> that.. and we don't want to overlap the copy..
>=20
> So, really, we need the tail to be larger than twice the mic.. less 1. =
 That
> means the fix is probably just increasing rslack for krb5i.

What's the justification for that particular maximum size? Are you sure =
the
page contents are not spilling into the tail?

--
Chuck Lever