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

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Date:   Tue, 10 Sep 2019 12:12:52 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Yunsheng Lin <linyunsheng@...wei.com>, 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, Sep 10, 2019 at 01:04:51PM +0200, Michal Hocko wrote:
> 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.

That seems reasonable to me, and much more "obvious" as to what is going
on.

thanks,

greg k-h