Messages in this thread | | | Date | Fri, 16 Aug 2013 12:45:44 -0400 | From | Tejun Heo <> | Subject | Re: [PATCH] print_worker_info: Handle pointer with more care |
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Hello,
On Fri, Aug 16, 2013 at 06:38:58PM +0200, Richard Weinberger wrote: > > 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()? > > You are already talking to UML people. ;)
Ooh... :)
> Anyway, I'll investigate into that. > What I see so far is that pwq is NULL after probe_kernel_read().
Yeah, and that should be fine. &pwq->wq would be just an offset of wq from NULL which is an invalid pointer but probe_kernel_read() should be able to handle that and probably just return 0 or -1 (all bits set). I *think* what's necessary is making probe_kernel_read() use mincore() to fine out whether the requested address is mapped (it should return -EFAULT if not) and try to dereference the address iff it's mapped.
Thanks.
-- tejun
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