linux-kernel - Re: [PATCH 3/3] Make jprobes a little safer for users

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20070625235103.2d8dea18.akpm@linux-foundation.org>
Date:	Mon, 25 Jun 2007 23:51:03 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	michael@...erman.id.au
Cc:	Christoph Hellwig <hch@....de>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org, linux-ia64@...r.kernel.org,
	linux-arch@...r.kernel.org, anil.s.keshavamurthy@...el.com,
	ananth@...ibm.com
Subject: Re: [PATCH 3/3] Make jprobes a little safer for users

On Tue, 26 Jun 2007 16:03:58 +1000 Michael Ellerman <michael@...erman.id.au> wrote:

> On Tue, 2007-06-26 at 07:53 +0200, Christoph Hellwig wrote:
> > On Tue, Jun 26, 2007 at 11:48:51AM +1000, Michael Ellerman wrote:
> > > I realise jprobes are a razor-blades-included type of interface, but
> > > that doesn't mean we can't try and make them safer to use. This guy I
> > > know once wrote code like this:
> > > 
> > > struct jprobe jp = { .kp.symbol_name = "foo", .entry = "jprobe_foo" };
> > > 
> > > And then his kernel exploded. Oops.
> > > 
> > > This patch adds an arch hook, arch_deref_entry_point() (I don't like it either)
> > > which takes the void * in a struct jprobe, and gives back the text address
> > > that it represents.
> > > 
> > > We can then use that in register_jprobe() to check that the entry point
> > > we're passed is actually in the kernel text, rather than just some random
> > > value.
> > 
> > Please don't add more weak functions, they're utterly horrible for
> > anyone trying to understand the code.  Otherwise this looks fine to me.
> 
> What do you recommend instead? #define ARCH_HAS_FOO_BAR ?

o lord, save us, no.

> I don't see what's utterly horrible about them.

Me either.

> The fact that they're
> weak is fairly reasonable documentation that they're overridden
> somewhere else. And grep/cscope/ctags will find both the weak and
> non-weak versions for you?

yup.

In this case we could just require that each jprobes-supporting
architecture implement arch_deref_entry_point().


Or one could do the Linus trick.  In each architecture which implements
arch_deref_entry_point() do:

#define arch_deref_entry_point arch_deref_entry_point

in the per-arch header file then, in non-arch code, do

#ifndef arch_deref_entry_point
static unsigned long arch_deref_entry_point(...)
{
	<generic implementation>
}
#endif

That's just the ARCH_HAS_FOO_BAR thing, only less fugly.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/