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Re: PROBLEM: null pointer dereference in cfq_dispatch_requests (2.6.21-rc2 and 2.6.20)

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From: Johannes Weiner
Subject: Re: PROBLEM: null pointer dereference in cfq_dispatch_requests (2.6.21-rc2 and 2.6.20)
Date: Wednesday, March 21, 2007 - 12:04 pm

Hi,

I think I found where the NULL may come from.  Please, anybody, do not
apply this patch before a trustful person reviewed it... Jens? ;)

My thoughts on this are, that there are two possibilities cfqq->next_rq
could be NULL: End of list or a bug when it is set (or not set).
But why does RB_EMPTY_ROOT() as last call in this loop does not trigger?

Did I even get the right place on where the NULL pointer dereference
happens? :)

=Hannes

Signed-off-by: Johannes Weiner <hannes-kernel@saeurebad.de>
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Messages in current thread:
Re: PROBLEM: null pointer dereference in , Dale Blount, (Wed Mar 21, 6:07 am)
Re: PROBLEM: null pointer dereference in cfq_dispatch_requ ..., Chuck Ebbert, (Wed Mar 21, 11:09 am)
Re: PROBLEM: null pointer dereference in cfq_dispatch_requ ..., Dale Blount, (Wed Mar 21, 11:23 am)
Re: PROBLEM: null pointer dereference in cfq_dispatch_requ ..., Chuck Ebbert, (Wed Mar 21, 11:25 am)
Re: PROBLEM: null pointer dereference in cfq_dispatch_requ ..., Johannes Weiner, (Wed Mar 21, 12:04 pm)
Re: PROBLEM: null pointer dereference in cfq_dispatch_requ ..., Jens Axboe, (Wed Mar 21, 12:59 pm)
Re: PROBLEM: null pointer dereference in cfq_dispatch_requ ..., Dale Blount, (Thu Mar 22, 5:54 am)
Re: PROBLEM: null pointer dereference in cfq_dispatch_requ ..., Johannes Weiner, (Thu Mar 22, 10:29 am)
Re: PROBLEM: null pointer dereference in cfq_dispatch_requ ..., Jens Axboe, (Thu Mar 22, 11:42 am)
Re: PROBLEM: null pointer dereference in cfq_dispatch_requ ..., Johannes Weiner, (Thu Mar 22, 12:22 pm)