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Date: Thu, 12 Oct 2017 13:24:08 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: Joe Perches <joe@...ches.com>
Cc: kernel-hardening@...ts.openwall.com, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org,
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>, Ian Campbell <ijc@...lion.org.uk>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.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>
Subject: Re: [PATCH] printk: hash addresses printed with %p
On Tue, Oct 10, 2017 at 09:06:50PM -0700, Joe Perches wrote:
> On Wed, 2017-10-11 at 14:48 +1100, Tobin C. Harding wrote:
> > Currently there are many places in the kernel where addresses are being
> > printed using an unadorned %p. Kernel pointers should be printed using
> > %pK allowing some control via the kptr_restrict sysctl. Exposing addresses
> > gives attackers sensitive information about the kernel layout in memory.
> []
> > diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> []
> > @@ -1591,6 +1591,35 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
> > return widen_string(buf, buf - buf_start, end, spec);
> > }
> >
> > +static long get_random_odd_long(void)
> > +{
> > + long val = 0;
> > +
> > + while((val & 1) == 0) {
> > + val = get_random_long();
> > + }
> > +
> > + return val;
> > +}
>
> Perhaps
>
> static long get_random_odd_long(void)
> {
> return get_random_long() | 1L;
> }
>
Nice.
thanks,
Tobin.
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