linux-kernel - Re: [PATCH] driver core: ensure a device has valid node id in device

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Message-ID: <20190910110451.GP2063@dhcp22.suse.cz>
Date:   Tue, 10 Sep 2019 13:04:51 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, rafael@...nel.org,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...nel.org, linuxarm@...wei.com
Subject: Re: [PATCH] driver core: ensure a device has valid node id in
 device_add()

On Tue 10-09-19 18:58:05, Yunsheng Lin wrote:
> On 2019/9/10 17:31, Greg KH wrote:
> > On Tue, Sep 10, 2019 at 02:43:32PM +0800, Yunsheng Lin wrote:
> >> On 2019/9/9 17:53, Greg KH wrote:
> >>> On Mon, Sep 09, 2019 at 02:04:23PM +0800, Yunsheng Lin wrote:
> >>>> Currently a device does not belong to any of the numa nodes
> >>>> (dev->numa_node is NUMA_NO_NODE) when the node id is neither
> >>>> specified by fw nor by virtual device layer and the device has
> >>>> no parent device.
> >>>
> >>> Is this really a problem?
> >>
> >> Not really.
> >> Someone need to guess the node id when it is not specified, right?
> > 
> > No, why?  Guessing guarantees you will get it wrong on some systems.
> > 
> > Are you seeing real problems because the id is not being set?  What
> > problem is this fixing that you can actually observe?
> 
> When passing the return value of dev_to_node() to cpumask_of_node()
> without checking the node id if the node id is not valid, there is
> global-out-of-bounds detected by KASAN as below:

OK, I seem to remember this being brought up already. And now when I
think about it, we really want to make cpumask_of_node NUMA_NO_NODE
aware. That means using the same trick the allocator does for this
special case.
-- 
Michal Hocko
SUSE Labs