Re: [PATCH 1/2] nfsd: fix type mismatch and explain host-endian xdr buffer usage

On Mon, Aug 3, 2026, at 12:23 PM, Jeff Layton wrote:
> On Mon, 2026-08-03 at 12:04 -0400, Chuck Lever wrote:

>> Number 3: Yes, we have a sordid history of grabbing a piece of
>> the xdr_buf's tail iov for temporary storage. That doesn't make
>> it wise to do, and assumes behavior about that buffer that is
>> not guaranteed by sunrpc's API contracts. That makes life hard
>> when future changes need to change that buffer to, say, a page
>> rather than kmalloc'd memory. Or when I want to convert this
>> code to use xdrgen instead of hand-rolled encoding.
>
> I had no idea this practice was suddenly forbidden. That has certainly
> not been communicated to me in any of the previous review rounds over
> the last couple of years.

I've been removing instances of this anti-pattern for some time. I
haven't seen new code (until now) that tries to do this. It simply
hasn't come up recently and I typically don't look closely for it.


>> So what you've done is fine for operational prototype code, but
>> not something we can carry forward as production code. The sparse
>> warning is a canary, it's not the actual structural problem.
>
> Does this mean you intend to drop dir delegation series again?

No. It's deep in nfsd-next now, and this is a long-term issue, not
an immediate on-the-wire behavioral problem or a vulnerability.


-- 
Chuck Lever