linux-kernel - Re: [PATCH 0/2] introduce DUMP_PREFIX

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Message-ID: <20210119014725.GH2260413@casper.infradead.org>
Date:   Tue, 19 Jan 2021 01:47:25 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Timur Tabi <timur@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        Petr Mladek <pmladek@...e.com>, roman.fietze@...na.com,
        keescook@...omium.org, Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>, linux-mm@...ck.org,
        Akinobu Mita <akinobu.mita@...il.com>
Subject: Re: [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps

On Tue, Jan 19, 2021 at 09:53:01AM +0900, Sergey Senozhatsky wrote:
> On (21/01/18 13:03), Timur Tabi wrote:
> > On 1/18/21 12:26 PM, Matthew Wilcox wrote:
> > > Don't make it easy.  And don't make it look like they're doing
> > > something innocent.  DUMP_PREFIX_SECURITY_HOLE would be OK
> > > by me.  DUMP_PREFIX_LEAK_INFORMATION would work fine too.
> > > DUMP_PREFIX_MAKE_ATTACKERS_LIFE_EASY might be a bit too far.
> > 
> > It's already extremely easy to replace %p with %px in your own printks, so I
> > don't really understand your argument.
> 
> I like the idea of a more radical name, e.g. DUMP_PREFIX_RAW_POINTERS or
> something similar.
> 
> > Seriously, this patch should not be so contentious.  If you want hashed
> > addresses, then nothing changes.  If you need unhashed addresses while
> > debugging, then use DUMP_PREFIX_UNHASHED.  Just like you can use %px in
> > printk.  I never use %p in my printks, but then I never submit code upstream
> > that prints addresses, hashed or unhashed.

I'm glad to hear you never make mistakes.  I make lots of mistakes, so
I prefer them to be big, loud and obvious so they're easy for people
to spot.

> So maybe DUMP_PREFIX_UNHASHED can do the unhashed dump only when
> CONFIG_DEBUG_KERNEL=y and fallback to DUMP_PREFIX_ADDRESS otherwise?

Distros enable CONFIG_DEBUG_KERNEL.  If you want to add
CONFIG_DEBUG_LEAK_ADDRESSES, then that's great, and you won't even have
to change users, you can just change how %p behaves.