netdev - Re: [PATCH net-next RFC 0/3] net: move .getsockopt away from _

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Message-ID: <20260131153735.3c9273a8@pumpkin>
Date: Sat, 31 Jan 2026 15:37:35 +0000
From: David Laight <david.laight.linux@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Breno Leitao <leitao@...ian.org>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
 <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, Willem de Bruijn
 <willemb@...gle.com>, metze@...ba.org, axboe@...nel.dk, Stanislav Fomichev
 <sdf@...ichev.me>, io-uring@...r.kernel.org, bpf@...r.kernel.org,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH net-next RFC 0/3] net: move .getsockopt away from __user
 buffers

On Fri, 30 Jan 2026 17:19:55 -0800
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Fri, 30 Jan 2026 at 14:40, David Laight <david.laight.linux@...il.com> wrote:
> >
> > There is not much point making the 'optval' parameter more than
> > a structure of a user and kernel address - one of which will be NULL.  
> 
> That's exactly what we do *NOT* want. Because people will get it
> wrong, and then we're back to the bad old days where trivial bugs
> result in security issues.

It can still be a (semi-)transparent structure that code isn't allowed to change.
That is no different from using iov_iter.

> Can you point to an actual case where setsockopt / getsockopt would be
> performance-critical? Typically you do it once or twice.

IIRC a really horrid one - I think for async io.
That is also one of the few where the supplied length is a lie.

	David

> 
>               Linus
>