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Message-ID: <20171113060807.GK11398@eros>
Date: Mon, 13 Nov 2017 17:08:07 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: kaiwan.billimoria@...il.com
Cc: kernel-hardening@...ts.openwall.com,
"Jason A. Donenfeld" <Jason@...c4.com>,
Theodore Ts'o <tytso@....edu>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Kees Cook <keescook@...omium.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Tycho Andersen <tycho@...ker.com>,
"Roberts, William C" <william.c.roberts@...el.com>,
Tejun Heo <tj@...nel.org>,
Jordan Glover <Golden_Miller83@...tonmail.ch>,
Greg KH <gregkh@...uxfoundation.org>,
Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>,
Ian Campbell <ijc@...lion.org.uk>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <wilal.deacon@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>,
Daniel Micay <danielmicay@...il.com>,
Djalal Harouni <tixxdz@...il.com>, linux-kernel@...r.kernel.org,
Network Development <netdev@...r.kernel.org>,
David Miller <davem@...emloft.net>
Subject: Re: [PATCH v4] scripts: add leaking_addresses.pl
On Mon, Nov 13, 2017 at 11:16:28AM +0530, kaiwan.billimoria@...il.com wrote:
> On Mon, 2017-11-13 at 09:21 +1100, Tobin C. Harding wrote:
> > On Fri, Nov 10, 2017 at 07:26:34PM +0530, kaiwan.billimoria@...il.com
> > wrote:
> > > On Tue, 2017-11-07 at 21:32 +1100, Tobin C. Harding wrote:
> > > > 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. On 32 kernels we don't have this luxury.
> > >
> > > Tobin C. Harding <me@...in.cc> wrote:
> > > > 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. On 32 kernels we don't have this luxury.
> > >
> > > [RFC] leaking_addresses.pl - enhance it to work for 32-bit kernels
> > > as well
> > >
> > > (Firstly, apologies if I've got the protocol horribly wrong- should
> > > this
> > > be a new thread altogether?)
> >
> > I think this patch will need to wait until the patch set that is
> > currently in flight is either merged or dropped.
> >
> Thanks for looking at it!
> Okay; blocking on merge || drop... :-)
So, Linus has requested that I set up a tree for the development of
this. I have to work out the details of how to do that and then I'll
email you so you can get the pull the current version. I can then take
your patch via LKML as per usual.
> > We can work this out pragmatically, Perl can give us an architecture
> > string then a few regexs can ascertain which architecture we are
> > running
> > on. This is in the inflight patch set.
> >
> > > The patch below does Not take into account (yet) stuff like:
> > > - exactly which files & dirs should be skipped on 32-bit (will it
> > > be
> > > identical to 64-bit?; unsure..)
> >
> > As per discussion later in this thread we may need to consider
> > architecture specific lists for files/directories to skip.
> Right
> >
> > > - it currently hard-codes a global 'PAGE_OFFSET_32BIT=0xc0000000'
> > > , just
> > > so I can test quickly; must figure whether to query it or pass it;
> > > Suggestions?
> >
> > Perhaps we should have a command line option for this.
> >
> > --kernel-base-address
>
> Why not just detect it programatically? We could devise a series of
> fallbacks; something like:
> - if .config exists in the kernel source tree root, grep it for
> PAGE_OFFSET
> - if not, grep the arch-specific (arch/<arch>/configs/<config-file>)
> for the same
> - if for some reason we don't have enough info regarding specific
> platform and thus the defconfig filename (could happen for ARM, PPC?),
> we then fail and request the user to pass it as a parameter.
>
> > > - the 'false positives'; again, what differs for 32-bit?
Sounds good to me.
thanks,
Tobin.
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