Re: [PATCH] busybox: add devmem

[Tom Rini <trini@konsulko.com>]

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On Wed, Jan 30, 2019 at 10:31:58PM +0000, Richard Purdie wrote:
> On Wed, 2019-01-30 at 14:18 -0800, Khem Raj wrote:
> > 
> > 
> > On Wed, Jan 30, 2019 at 12:31 PM Adrian Bunk <bunk@stusta.de> wrote:
> > > On Wed, Jan 30, 2019 at 08:50:02AM -0800, Khem Raj wrote:
> > > > On Wed, Jan 30, 2019 at 1:34 AM Adrian Bunk <bunk@stusta.de>
> > > wrote:
> > > > >
> > > > > This is a tiny but pretty useful tool.
> > > > >
> > > > 
> > > > question is, do we need this enabled in default config, or could
> > > be add it via
> > > > some DISTRO_FEATURE meant for validation etc. May be if you
> > > explain your
> > > > usecase then we might be able to make a better assessment.
> > > 
> > > Sorry for being too terse.
> > > 
> > > devmem allows reading and writing hardware configuration registers,
> > > which is useful both for debugging and for scripts.
> > > 
> > 
> > Thanks for the info this seems useful can you also report how much
> > does it increase size of busybox 
> 
> One reason I'm a little nervous of devmem in busybox is security attack
> surface. You can of course argue that there are 101 ways to mimic
> devmem so this isn't a concern. When you consider some configurations
> can have suid busybox, it becomes more of a worry. Our default
> separates out the suid pieces for the attack surface reason.
> 
> It is useful so I am torn but its worth keeping this in mind...

I would also ask if we should be enabling more stuff in busybox, period.
Customizing busybox for what you're trying to _do_ with a custom setup
is one of those top 5 TODO items with making a cut down image and
customizing the kernel config.  Outside of -tiny and initramfs/similar
cases, there's not a great reason to use
almost-but-not-quite-complete-busybox-applet compared with the regular
app.

-- 
Tom

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