From: Steffen Trumtrar <s.trumtrar@pengutronix.de>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>,
Jens Axboe <axboe@kernel.dk>, Paolo Abeni <pabeni@redhat.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
kernel@pengutronix.de
Subject: Re: [PATCH] net: Do not break out of sk_stream_wait_memory() with TIF_NOTIFY_SIGNAL
Date: Tue, 19 Dec 2023 12:00:44 +0100 [thread overview]
Message-ID: <87cyv2wj4e.fsf@pengutronix.de> (raw)
In-Reply-To: <20231117-starter-unvisited-d10f0314ae76-mkl@pengutronix.de>
On 2023-11-17 at 11:43 +01, Marc Kleine-Budde <mkl@pengutronix.de> wrote:
> [[PGP Signed Part:Undecided]]
> On 27.10.2023 14:04:32, Sascha Hauer wrote:
>> On Thu, Oct 26, 2023 at 10:49:18AM +0200, Paolo Abeni wrote:
>> > On Thu, 2023-10-26 at 09:03 +0200, Sascha Hauer wrote:
>> > > On Tue, Oct 24, 2023 at 03:56:17PM +0200, Paolo Abeni wrote:
>> > > > On Mon, 2023-10-23 at 14:13 +0200, Sascha Hauer wrote:
>> > > > > It can happen that a socket sends the remaining data at close() time.
>> > > > > With io_uring and KTLS it can happen that sk_stream_wait_memory() bails
>> > > > > out with -512 (-ERESTARTSYS) because TIF_NOTIFY_SIGNAL is set for the
>> > > > > current task. This flag has been set in io_req_normal_work_add() by
>> > > > > calling task_work_add().
>> > > > >
>> > > > > It seems signal_pending() is too broad, so this patch replaces it with
>> > > > > task_sigpending(), thus ignoring the TIF_NOTIFY_SIGNAL flag.
>> > > >
>> > > > This looks dangerous, at best. Other possible legit users setting
>> > > > TIF_NOTIFY_SIGNAL will be broken.
>> > > >
>> > > > Can't you instead clear TIF_NOTIFY_SIGNAL in io_run_task_work() ?
>> > >
>> > > I don't have an idea how io_run_task_work() comes into play here, but it
>> > > seems it already clears TIF_NOTIFY_SIGNAL:
>> > >
>> > > static inline int io_run_task_work(void)
>> > > {
>> > > /*
>> > > * Always check-and-clear the task_work notification signal. With how
>> > > * signaling works for task_work, we can find it set with nothing to
>> > > * run. We need to clear it for that case, like get_signal() does.
>> > > */
>> > > if (test_thread_flag(TIF_NOTIFY_SIGNAL))
>> > > clear_notify_signal();
>> > > ...
>> > > }
>> >
>> > I see, io_run_task_work() is too late, sk_stream_wait_memory() is
>> > already woken up.
>> >
>> > I still think this patch is unsafe. What about explicitly handling the
>> > restart in tls_sw_release_resources_tx() ? The main point is that such
>> > function is called by inet_release() and the latter can't be re-
>> > started.
>>
>> I don't think there's anything I can do in tls_sw_release_resources_tx().
>> When entering this function TIF_NOTIFY_SIGNAL is not (yet) set. It gets
>> set at some point while tls_sw_release_resources_tx() is running. I find
>> it set when tls_tx_records() returns with -ERESTARTSYS. I tried clearing
>> TIF_NOTIFY_SIGNAL then and called tls_tx_records() again, but that doesn't
>> work.
>
> Seems the discussion got stuck, what are the blocking points?
Ping!
Any pointers on how to get this sorted out?
Best regards,
Steffen
--
Pengutronix e.K. | Dipl.-Inform. Steffen Trumtrar |
Steuerwalder Str. 21 | https://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686| Fax: +49-5121-206917-5555 |
next prev parent reply other threads:[~2023-12-19 11:02 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-23 12:13 [PATCH] net: Do not break out of sk_stream_wait_memory() with TIF_NOTIFY_SIGNAL Sascha Hauer
2023-10-24 13:56 ` Paolo Abeni
2023-10-26 7:03 ` Sascha Hauer
2023-10-26 8:49 ` Paolo Abeni
2023-10-27 12:04 ` Sascha Hauer
2023-11-17 10:43 ` Marc Kleine-Budde
2023-12-19 11:00 ` Steffen Trumtrar [this message]
2023-12-19 13:13 ` Paolo Abeni
2024-03-15 10:01 Sascha Hauer
2024-03-15 16:43 ` Jens Axboe
2024-03-15 17:02 ` Pavel Begunkov
2024-03-18 12:10 ` Sascha Hauer
2024-03-18 13:19 ` Pavel Begunkov
2024-03-19 10:50 ` Sascha Hauer
2024-03-19 13:55 ` Pavel Begunkov
2024-03-19 15:08 ` Sascha Hauer
2024-03-18 12:03 ` Sascha Hauer
2024-03-19 12:30 ` Paolo Abeni
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