linux-kernel - Re: [PATCH net] can: isotp: isotp_rcv

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 7 Feb 2022 09:11:23 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Oliver Hartkopp <socketcan@...tkopp.net>
Cc:     "Ziyang Xuan (William)" <william.xuanziyang@...wei.com>,
        davem@...emloft.net, kuba@...nel.org, linux-can@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] can: isotp: isotp_rcv_cf(): fix so->rx race problem

On 28.01.2022 15:48:05, Oliver Hartkopp wrote:
> Hello Marc, hello William,
> 
> On 28.01.22 09:46, Marc Kleine-Budde wrote:
> > On 28.01.2022 09:32:40, Oliver Hartkopp wrote:
> > > 
> > > 
> > > On 28.01.22 09:07, Marc Kleine-Budde wrote:
> > > > On 28.01.2022 08:56:19, Oliver Hartkopp wrote:
> > > > > I've seen the frame processing sometimes freezes for one second when
> > > > > stressing the isotp_rcv() from multiple sources. This finally freezes
> > > > > the entire softirq which is either not good and not needed as we only
> > > > > need to fix this race for stress tests - and not for real world usage
> > > > > that does not create this case.
> > > > 
> > > > Hmmm, this doesn't sound good. Can you test with LOCKDEP enabled?
> 
> 
> > > #
> > > # Lock Debugging (spinlocks, mutexes, etc...)
> > > #
> > > CONFIG_LOCK_DEBUGGING_SUPPORT=y
> > > # CONFIG_PROVE_LOCKING is not set
> > CONFIG_PROVE_LOCKING=y
> 
> Now enabled even more locking (seen relevant kernel config at the end).
> 
> It turns out that there is no visible difference when using spin_lock() or
> spin_trylock().
> 
> I only got some of these kernel log entries
> 
> Jan 28 11:13:14 silver kernel: [ 2396.323211] perf: interrupt took too long
> (2549 > 2500), lowering kernel.perf_event_max_sample_rate to 78250
> Jan 28 11:25:49 silver kernel: [ 3151.172773] perf: interrupt took too long
> (3188 > 3186), lowering kernel.perf_event_max_sample_rate to 62500
> Jan 28 11:45:24 silver kernel: [ 4325.583328] perf: interrupt took too long
> (4009 > 3985), lowering kernel.perf_event_max_sample_rate to 49750
> Jan 28 12:15:46 silver kernel: [ 6148.238246] perf: interrupt took too long
> (5021 > 5011), lowering kernel.perf_event_max_sample_rate to 39750
> Jan 28 13:01:45 silver kernel: [ 8907.303715] perf: interrupt took too long
> (6285 > 6276), lowering kernel.perf_event_max_sample_rate to 31750
> 
> But I get these sporadically anyway. No other LOCKDEP splat.
> 
> At least the issue reported by William should be fixed now - but I'm still
> unclear whether spin_lock() or spin_trylock() is the best approach here in
> the NET_RX softirq?!?

With the !spin_trylock() -> return you are saying if something
concurrent happens, drop it. This doesn't sound correct.

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)