linux-kernel - Re: [PATCH V8 0/2] printk: hash addresses printed with %p

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Date:   Thu, 2 Nov 2017 17:23:44 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     "Tobin C. Harding" <me@...in.cc>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        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>,
        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
Subject: Re: [PATCH V8 0/2] printk: hash addresses printed with %p

On (11/01/17 10:35), Tobin C. Harding wrote:
[..]
> Yes. The question has been raised will we be here again in 6 years time
> trying to fix all the uses of %x. And there are already 29K uses of
> %[xX] in tree, which of these are leaking addresses? This is why Linus'
> has commented that really effort should be directed at finding the leaks
> as they happen (in procfs, sysfs, dmesg) instead of fixing this in
> the code.

got it. thanks.

> So far I haven't been able to come up with any meaningful way
> to do this on 32 bit machines. There is a patch adding a script to catch
> leaks on 64 bit machines in flight.

who is expected to run that script?

BTW, can BPF/eBPF printk addresses?

> This patch needs to be a small part of a continued effort to stop the
> leaks if we want to have any hope of stopping them.
> 
> If you have any suggestions on dealing with %x please do say. We have
> code changes, compiler warnings, and checkpatch - none of which
> immediately seem great.

hm... just a huge pile of if's

	if (is_vmalloc_addr(addr))
		do_hashing(addr);
	else if (__module_address(addr))
		do_hashing(addr);
	else if (is_kernel(addr) || is_kernel_inittext(addr))
	...

but that's going to be really messy and "iffy".

	-ss