linux-kernel - Re: [PATCH v2 08/11] tty: splice

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Message-Id: <2XFP6S.GINKQ8IKAA1W1@gmail.com>
Date: Thu, 04 Jan 2024 10:34:14 +1300
From: Oliver Giles <ohw.giles@...il.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Jiri Slaby <jirislaby@...nel.org>, Ahelenia Ziemiańska
	<nabijaczleweli@...ijaczleweli.xyz>, Jens Axboe <axboe@...nel.dk>,
	Christian Brauner <brauner@...nel.org>, Alexander Viro
	<viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 08/11] tty: splice_read: disable


On Wed, Jan 3 2024 at 11:14:59 -08:00:00, Linus Torvalds 
<torvalds@...ux-foundation.org> wrote:
> 
> It's some annoying SSL VPN thing that splices to pppd:
> 
>    https://lore.kernel.org/all/C8KER7U60WXE.25UFD8RE6QZQK@oguc/

I'm happy to report that that particular SSL VPN tool is no longer 
around.
And it had anyway grown a fall-back-to-read/write in case splice() 
fails.
So at least from my perspective, no objections to splice-to-tty going 
away
altogether.

> and I'd be happy to try to limit splice to tty's to maybe just the one
> case that pppd uses.

To be exact, pppd is just providing a pty with which other (now all 
extinct?)
applications can do nefarious things.

> Maybe that VPN thing already has the pty in non-blocking mode, for
> example, and we could make the tty splicing fail for any blocking op?

FWIW, the SSL VPN tool did indeed have the pty in non-blocking mode.

Oliver