Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.33 as permitted sender) client-ip=23.128.96.33;
Date:   Fri, 17 Nov 2023 11:43:21 +0100
From:   Marc Kleine-Budde <mkl@pengutronix.de>
To:     Sascha Hauer <s.hauer@pengutronix.de>,
        Jens Axboe <axboe@kernel.dk>, Paolo Abeni <pabeni@redhat.com>
Cc:     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
Message-ID: <20231117-starter-unvisited-d10f0314ae76-mkl@pengutronix.de>
References: <20231023121346.4098160-1-s.hauer@pengutronix.de>
 <addf492843338e853f7fda683ce35050f26c9da0.camel@redhat.com>
 <20231026070310.GY3359458@pengutronix.de>
 <8404022493c5ceda74807a3407e5a087425678e2.camel@redhat.com>
 <20231027120432.GB3359458@pengutronix.de>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
        protocol="application/pgp-signature"; boundary="myrtppjg3pcf7ghi"
Content-Disposition: inline
In-Reply-To: <20231027120432.GB3359458@pengutronix.de>
Precedence: bulk


--myrtppjg3pcf7ghi
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

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() t=
ime.
> > > > > 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().
> > > > >=20
> > > > > It seems signal_pending() is too broad, so this patch replaces it=
 with
> > > > > task_sigpending(), thus ignoring the TIF_NOTIFY_SIGNAL flag.
> > > >=20
> > > > This looks dangerous, at best. Other possible legit users setting
> > > > TIF_NOTIFY_SIGNAL will be broken.
> > > >=20
> > > > Can't you instead clear TIF_NOTIFY_SIGNAL in io_run_task_work() ?
> > >=20
> > > I don't have an idea how io_run_task_work() comes into play here, but=
 it
> > > seems it already clears TIF_NOTIFY_SIGNAL:
> > >=20
> > > 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 not=
hing to
> > >          * run. We need to clear it for that case, like get_signal() =
does.
> > >          */
> > >         if (test_thread_flag(TIF_NOTIFY_SIGNAL))
> > >                 clear_notify_signal();
> > > 	...
> > > }
> >=20
> > I see, io_run_task_work() is too late, sk_stream_wait_memory() is
> > already woken up.
> >=20
> > 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.
>=20
> 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?

Marc

--=20
Pengutronix e.K.                 | Marc Kleine-Budde          |
Embedded Linux                   | https://www.pengutronix.de |
Vertretung N=C3=BCrnberg              | Phone: +49-5121-206917-129 |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-9   |

--myrtppjg3pcf7ghi
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----

iQEzBAABCgAdFiEEDs2BvajyNKlf9TJQvlAcSiqKBOgFAmVXQ8YACgkQvlAcSiqK
BOjTBAf/bx31f+dylh6QTDp4+y9R5QW/hooHn72DH7PdipTn0Sn/N85TT/6dwm2m
d6zrmYaYoORvTMvxkDNuvlPI3Ye8x1s03XmRdUzZz42lktKlwL7vx+WNPofcsuYv
OSZBM7DnLPZzd04gCfME5+Z0F8ja7qFW/TeFLMNaTdA15hNmrtql/dNnxQ8rOcFi
QGSYH0Hukk9WCBVsJfWh1TUD7ofi+W4kEXVoJudKhMacz6U1m2hqwzsCHZl4MfBw
Hy15O4ShNqgYhGonRLk6GKvZp0UcrP9vupIgFuAz2tQIss7IlukeYEj/K+1yERXC
oENATOsMpTHZwnHiYEqD59Iwj2jCSA==
=4VsN
-----END PGP SIGNATURE-----

--myrtppjg3pcf7ghi--