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Date: Thu, 9 Apr 2020 22:56:57 +0300
From: Alexander Popov <alex.popov@...ux.com>
To: Julia Lawall <julia.lawall@...ia.fr>
Cc: Gilles Muller <Gilles.Muller@...6.fr>,
Nicolas Palix <nicolas.palix@...g.fr>, Michal Marek
<michal.lkml@...kovi.net>, cocci@...teme.lip6.fr,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Jann Horn <jannh@...gle.com>, Kees Cook <keescook@...omium.org>,
Hans Verkuil <hverkuil@...all.nl>, Mauro Carvalho Chehab
<mchehab@...nel.org>, Linux Media Mailing List
<linux-media@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
Markus Elfring <Markus.Elfring@....de>
Subject: Re: [Cocci] Coccinelle rule for CVE-2019-18683
On 09.04.2020 13:53, Julia Lawall wrote:
> On Thu, 9 Apr 2020, Alexander Popov wrote:
>> virtual report
>>
>> @race exists@
>> expression E;
>> position stop_p;
>> position unlock_p;
>> position lock_p;
>> @@
>>
>> mutex_unlock@...ock_p(E)
>> ...
>
> It would be good to put when != mutex_lock(E) after the ... above. Your
> rule doesn't actually prevent the lock from being retaken.
Thanks Julia! I used this trick in the second version of the rule that I've just
sent.
>> kthread_stop@...p_p(...)
>> ...
>> mutex_lock@...k_p(E)
>>
>> @script:python@
>> stop_p << race.stop_p;
>> unlock_p << race.unlock_p;
>> lock_p << race.lock_p;
>> E << race.E;
>> @@
>>
>> coccilib.report.print_report(unlock_p[0], 'mutex_unlock(' + E + ') here')
>> coccilib.report.print_report(stop_p[0], 'kthread_stop here')
>> coccilib.report.print_report(lock_p[0], 'mutex_lock(' + E + ') here\n')
...
> Based on Jann's suggestion, it seem like it could be interesting to find
> these locking pauses, and then collect functions that are used in locks
> and in lock pauses. If a function is mostly used with locks held, then
> using it in a lock pause could be a sign of a bug. I will see if it turns
> up anything interesting.
Do you mean collecting the behaviour that happens between unlocking and locking
and then analysing it somehow?
Best regards,
Alexander
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