linux-kernel - Re: [PATCH v2 03/28] vsprintf: %pf(%p)

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: <20220520175645.bdv6zsenrqutywlc@moria.home.lan>
Date:   Fri, 20 May 2022 13:56:45 -0400
From:   Kent Overstreet <kent.overstreet@...il.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...r.kernel.org,
        pmladek@...e.com, rostedt@...dmis.org, senozhatsky@...omium.org,
        andriy.shevchenko@...ux.intel.com, willy@...radead.org
Subject: Re: [PATCH v2 03/28] vsprintf: %pf(%p)

On Fri, May 20, 2022 at 09:40:24AM +0200, Michal Hocko wrote:
> On Thu 19-05-22 13:23:56, Kent Overstreet wrote:
> [...]
> > The goal is to replace most of our %p format extensions with this
> > interface, and to move pretty-printers out of the core vsprintf.c code -
> > this will get us better organization and better discoverability (you'll
> > be able to cscope to pretty printer calls!), as well as eliminate a lot
> > of dispatch code in vsprintf.c.
> 
> Is this really something that we want? While I do see arguments about
> our existing %p$FOO mess there is at least one good argument to have all
> those "pretty printers" at a single location. That approach allows to do
> a proper review whether those printers are safe from the printk point of
> view. If we allow any random callback to be called from the printk
> context we just give a free ticket to anybody to do whatever from there
> without understanding of all potential consequences. 
> 
> Maybe that is less of a concern these days when printk locking has been
> reworked a lot but I still do remember how frustrating it is to debug
> issues related to printk getting stuck...

So for now, I added a note in the documentation that pretty-printers may not
sleep if passed to printk() - but if they're just passed to pr_buf() or
sprintf() it's completely fine.