Re: [PATCH] spi: expose spi_master and spi_device statistics via sysfs

[Martin Sperl <kernel@xxxxxxxxxxxxxxxx>]

> On 03.06.2015, at 13:53, Mark Brown <broonie@xxxxxxxxxx> wrote:
> 
>> On Wed, Jun 03, 2015 at 01:25:58PM +0200, Lars-Peter Clausen wrote:
>> 
>> Having those kinds of stats in world readable files has serious security
>> implications as they can be used to implement side-channel attacks. They
>> should probably only be available in debugfs for root.
> 
> We do get to control the permissions on sysfs files, though it's a bit
> more unusual to make things root only (and there is the histogram).

I left histogram as a single file because I remember having seen a file in
/sys with similar semantics using multiple values (but I can not
remember which one).

I can remove it when I get back near my development box in a little
more than a week.

As for side channel attacks: the information is there already.
E.g the number of Interrupts for the spi device in /proc/interrupts
This could also be used as an indicator for the number of spi 
transfers handled, so I do not see a huge difference...

If you want it as root only - we can do it, but I wonder if it is
making a real difference...


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