linux-kernel - Re: [PATCH] print_worker_info: Handle pointer with more care

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Message-ID: <20130816162844.GJ2505@htj.dyndns.org>
Date:	Fri, 16 Aug 2013 12:28:44 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Richard Weinberger <richard@....at>
Cc:	linux-kernel@...r.kernel.org, Jeff Dike <jdike@...toit.com>,
	Richard Weinberger <richard@....at>,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: [PATCH] print_worker_info: Handle pointer with more care

On Fri, Aug 16, 2013 at 06:15:07PM +0200, Richard Weinberger wrote:
> On UML I hit the case that pwq is NULL.
> Then we oops at &pwq->wq...

Hmmm?  I'm confused.  &pwq->wq is pwq's pointer + wq's offset in pwq.
It doesn't involve dereferencing pwq->wq.  Maybe uml isn't
implementing probe_kernel_thread()?  Now that I think about it, I'm
not sure how it could.

cc'ing uml people.  Hey, guys, workqueue uses proble_kernel_read() to
print out workqueue related information during oops because those
events are completely asynchronous and workqueue states may not be
consistently accessible.  It seems like uml doesn't implement
probe_kernel_read() and tries direct derference of incorrect pointers
leading to its own oops.  Maybe uml should check whether the memory is
mapped from probe_kernel_read()?

Thanks.

-- 
tejun
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