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Message-ID: <20171018060406.GA28753@eros>
Date: Wed, 18 Oct 2017 17:04:06 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc: kernel-hardening@...ts.openwall.com,
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 <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>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] printk: hash addresses printed with %p
On Wed, Oct 18, 2017 at 02:44:31PM +0900, Sergey Senozhatsky wrote:
> On (10/18/17 15:21), Tobin C. Harding wrote:
> [..]
> > diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> > index 86c3385b9eb3..4609738cd2cd 100644
> > --- a/lib/vsprintf.c
> > +++ b/lib/vsprintf.c
> > @@ -33,6 +33,8 @@
> > #include <linux/uuid.h>
> > #include <linux/of.h>
> > #include <net/addrconf.h>
> > +#include <linux/siphash.h>
> > +#include <linux/spinlock.h>
> > #ifdef CONFIG_BLOCK
> > #include <linux/blkdev.h>
> > #endif
> > @@ -1591,6 +1593,70 @@ char *device_node_string(char *buf, char *end, struct device_node *dn,
> > return widen_string(buf, buf - buf_start, end, spec);
> > }
> >
> > +/* protects ptr_secret and have_key */
> > +DEFINE_SPINLOCK(key_lock);
> > +static siphash_key_t ptr_secret __read_mostly;
> > +static atomic_t have_key = ATOMIC_INIT(0);
> > +
> > +static int initialize_ptr_secret(void)
> > +{
> > + spin_lock(&key_lock);
> > + if (atomic_read(&have_key) == 1)
> > + goto unlock;
> > +
> > + get_random_bytes(&ptr_secret, sizeof(ptr_secret));
> > + atomic_set(&have_key, 1);
> > +
> > +unlock:
> > + spin_unlock(&key_lock);
> > + return 0;
> > +}
>
> is this spinlock legal? what happens if we are getting interrupted by NMI?
I think we can do without the spinlock. I think I was already told that when
I tried to put it [some where else] in v1.
It's fun failing in public ;)
> printk()
> vprintk_emit()
> vscnprintf()
> pointer()
> ptr_to_id()
> initialize_ptr_secret()
> spin_lock(&key_lock)
>
> ----> NMI
>
> printk()
> printk_safe_log_store()
> vscnprintf()
> pointer()
> ptr_to_id()
> initialize_ptr_secret()
> spin_lock(&key_lock) <<<<
>
>
> or am I completely misreading the patch? sorry if so.
>
> -ss
thanks,
Tobin.
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