Re: Regression in 5.1.20: Reading long directory fails

From: Chuck Lever
Date: Wed Sep 11 2019 - 13:46:18 EST

> On Sep 11, 2019, at 1:40 PM, Benjamin Coddington <bcodding@xxxxxxxxxx> wrote:
> On 11 Sep 2019, at 13:29, Chuck Lever wrote:
>>> On Sep 11, 2019, at 1:26 PM, Benjamin Coddington <bcodding@xxxxxxxxxx> wrote:
>>> On 11 Sep 2019, at 12:39, Chuck Lever wrote:
>>>>> On Sep 11, 2019, at 12:25 PM, Benjamin Coddington <bcodding@xxxxxxxxxx> wrote:
>>>>> Instead, I think we want to make sure the mic falls squarely into the tail
>>>>> every time.
>>>> 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?
>>> Is it too niave to always put the mic at the end of the tail?
>> The size of the page content is variable.
>> 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.
> 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".
> 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..
> 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