linux-kernel - Re: [PATCH] net: wireless: iwlegacy: Fix possible data races in il4965_send_rxon

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Message-ID: <20181005075403.GC1931@redhat.com>
Date:   Fri, 5 Oct 2018 09:54:04 +0200
From:   Stanislaw Gruszka <sgruszka@...hat.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     kvalo@...eaurora.org, davem@...emloft.net,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: wireless: iwlegacy: Fix possible data races in
 il4965_send_rxon_assoc()

On Thu, Oct 04, 2018 at 04:52:19PM +0800, Jia-Ju Bai wrote:
> On 2018/10/4 15:59, Stanislaw Gruszka wrote:
> >On Wed, Oct 03, 2018 at 10:07:45PM +0800, Jia-Ju Bai wrote:
> >>These possible races are detected by a runtime testing.
> >>To fix these races, the mutex lock is used in il4965_send_rxon_assoc()
> >>to protect the data.
> >Really ? I'm surprised by that, see below.
> 
> My runtime testing shows that il4965_send_rxon_assoc() and
> il4965_configure_filter() are concurrently executed.
> But after seeing your reply, I need to carefully check whether my
> runtime testing is right, because I think you are right.
> In fact, I only monitored the iwl4965 driver, but did not monitor
> the iwlegacy driver, so I will do the testing again with monitoring
> the lwlegacy driver.
<snip>
> >So I wonder how this patch did not cause the deadlock ?
> 
> Oh, sorry, anyway, my patch will cause double locks...

So how those runtime test were performend such you didn't
notice this ?

> >Anyway what can be done is adding:
> >
> >lockdep_assert_held(&il->mutex);
> >
> >il4965_commit_rxon() to check if we hold the mutex.
> 
> I agree.

Care to post a patch ?

Thanks
Stanislaw