linux-kernel - Re: [PATCH V2 09/10] kasan: Prevent deadlock in kasan reporting

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Message-ID: <8737z1q6oh.fsf@linux.vnet.ibm.com>
Date:	Sun, 30 Aug 2015 18:23:02 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	paulus@...ba.org, mpe@...erman.id.au,
	linuxppc-dev@...ts.ozlabs.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 09/10] kasan: Prevent deadlock in kasan reporting

Andrey Ryabinin <ryabinin.a.a@...il.com> writes:

> 2015-08-26 11:26 GMT+03:00 Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>:
>> We we end up calling kasan_report in real mode, our shadow mapping
>> for even spinlock variable will show poisoned.
>
> Generally I agree with this patch. We should disable reports when we
> print report as early
> as possible to prevent recursion in case of bug in spinlock or printk etc.
>
> But I don't understand what is the problem that you observing.
> How we ended up with shadow poisoned for a valid spinlock struct?
> And since  shadow poisoned for some valid memory we should get
> enormous amount of false positive reports.
>

I still haven't fully isolated all the .c files which should not be
kasan instrumented. That means in case of ppc64 i ended up calling
kasan _load/_store in real mode. That will result in failure w.r.t
to the above spin_lock code.

-aneesh

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