On Wed, Nov 08, 2017 at 11:10:56PM +1100, Michael Ellerman wrote:
> "Tobin C. Harding" <m...@tobin.cc> writes:
> > Currently we are leaking addresses from the kernel to user space. This
> > script is an attempt to find some of those leakages. Script parses
> > `dmesg` output and /proc and /sys files for hex strings that look like
> > kernel addresses.
> >
> > Only works for 64 bit kernels, the reason being that kernel addresses
> > on 64 bit kernels have 'ffff' as the leading bit pattern making greping
> > possible.
>
> That doesn't work super well on other architectures :D
>
> I don't speak perl but presumably you can check the arch somehow and
> customise the regex?
I'm on it.
> ...
> > +# Return _all_ non false positive addresses from $line.
> > +sub extract_addresses
> > +{
> > + my ($line) = @_;
> > + my $address = '\b(0x)?ffff[[:xdigit:]]{12}\b';
>
> On 64-bit powerpc (ppc64/ppc64le) we'd want:
>
> + my $address = '\b(0x)?[89abcdef]00[[:xdigit:]]{13}\b';
This is great! Thanks a million. This gives me the idea of getting in
contact with people who have access to other [64 bit] architectures and
getting the address format. I guess a dump of kallsyms from each
architecture would do the job nicely.
> > +# Do not parse these files (absolute path).
> > +my @skip_parse_files_abs = ('/proc/kmsg',
> > + '/proc/kcore',
> > + '/proc/fs/ext4/sdb1/mb_groups',
> > + '/proc/1/fd/3',
> > + '/sys/kernel/debug/tracing/trace_pipe',
> > + '/sys/kernel/security/apparmor/revision');
>
> Can you add:
>
> /sys/firmware/devicetree
>
> and/or /proc/device-tree (which is a symlink to the above).
Can do, thanks.
> We should also start restricting access to that because it may have
> potentially interesting physical addresses in it, but that will break
> existing tools, so it will need to be opt-in and done over time.
Seems like this is going to be a recurring theme if we try to stop leaks
using file permissions. I'm interested in how we would do this, assuming
it has to be a case by case fix but done many times.
thanks,
Tobin.
