RE: [PATCH 1/2] topology: use bin_attribute to avoid buff overflow

[Song Bao Hua (Barry Song)]

> -----Original Message-----
> From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx]
> Sent: Tuesday, June 1, 2021 4:59 PM
> To: tiantao (H) <tiantao6@xxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; Song Bao Hua
> (Barry Song) <song.bao.hua@xxxxxxxxxxxxx>; Andy Shevchenko
> <andriy.shevchenko@xxxxxxxxxxxxxxx>; Rafael J. Wysocki <rafael@xxxxxxxxxx>
> Subject: Re: [PATCH 1/2] topology: use bin_attribute to avoid buff overflow
> 
> On Tue, Jun 01, 2021 at 10:56:49AM +0800, Tian Tao wrote:
> > Reading sys/devices/system/cpu/cpuX/topology/ returns cpu topology.
> > However, the size of this file is limited to PAGE_SIZE because of the
> > limitation for sysfs attribute. so we use bin_attribute instead of
> > attribute to avoid NR_CPUS too big to cause buff overflow.
> >
> > This patch is based on the following discussion.
> > https://www.spinics.net/lists/linux-doc/msg95921.html
> 
> Please use lore.kernel.org for links as we have no control over other
> sites to ensure that they will work in the future.  Use the message id
> in the link as well, so that if something were to happen to lore, we can
> figure it out.
> 
> Also, you are modifying a bunch of different files here, do you mean to
> do it for all of them?

The plan is providing a common wrapper similar with cpumap_print_to_pagebuf
so that all modules which have bitmap and list topology ABI can move to use
it.

Right now, drivers/base/topology.c and drivers/base/node.c are the first
two examples involved. We are still having around 40 other places in
the todo list.

Thanks
Barry