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

On Mon, 2007-06-25 at 19:00 -0700, Andrew Morton wrote:

On Tue, 26 Jun 2007 11:48:51 +1000 (EST) Michael Ellerman [off-list ref] wrote:

quoted

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.

Signed-off-by: Michael Ellerman <redacted>
---
 arch/ia64/kernel/kprobes.c    |    7 ++++++-
 arch/powerpc/kernel/kprobes.c |   11 ++++++++---
 kernel/kprobes.c              |    9 +++++++++

We're missing a declaration of arch_deref_entry_point() in some header file?

Yeah I guess. It's declared weak in kernel/kprobes.c, but there should
be a definition somewhere to make sure the three versions don't get out
of sync. I'll send a patch.

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person