netdev - Re: [PATCH] tls: defer close to kernel task

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Date: Fri, 12 Apr 2024 09:25:37 +0200
From: Sascha Hauer <s.hauer@...gutronix.de>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Boris Pismenny <borisp@...dia.com>,
	John Fastabend <john.fastabend@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Pavel Begunkov <asml.silence@...il.com>,
	Jens Axboe <axboe@...nel.dk>, kernel@...gutronix.de
Subject: Re: [PATCH] tls: defer close to kernel task

On Wed, Apr 10, 2024 at 06:11:28AM -0700, Jakub Kicinski wrote:
> On Wed, 10 Apr 2024 08:33:07 +0200 Sascha Hauer wrote:
> > proto->close is normally called from a userspace task which can be
> > interrupted by signals. When asynchronous encryption is used then KTLS
> > sends out the final data at close time. When a signal comes in during
> > close then it can happen tcp_sendmsg_locked() is interrupted by that
> > signal while waiting for memory in sk_stream_wait_memory() which then
> > returns with -ERSTARTSYS. It is not possible to recover from this situation
> > and the final transmit data is lost.
> > 
> > With this patch we defer the close operation to a kernel task which
> > doesn't get signals.
> > 
> > The described situation happens when KTLS is used in conjunction with
> > io_uring, as io_uring uses task_work_add() to add work to the current
> > userspace task.
> > 
> > The problem is discussed in [1] and [2] and the solution implemented in
> > this patch is suggested by Pavel Begunkov here [3]
> 
> Appears to crash reliably.
> Please run the tls selftests with KASAN enabled.

Oops, will run the tests and fix the fallout before resending.

Sascha

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