From: Kees Cook <keescook@chromium.org>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Timur Tabi <timur@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
Petr Mladek <pmladek@suse.com>,
roman.fietze@magna.com, Steven Rostedt <rostedt@goodmis.org>,
John Ogness <john.ogness@linutronix.de>,
linux-mm@kvack.org, Akinobu Mita <akinobu.mita@gmail.com>
Subject: Re: [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps
Date: Tue, 19 Jan 2021 11:45:49 -0800 [thread overview]
Message-ID: <202101191145.FE17081@keescook> (raw)
In-Reply-To: <YAa2oCNWjExWlQTu@jagdpanzerIV.localdomain>
On Tue, Jan 19, 2021 at 07:38:24PM +0900, Sergey Senozhatsky wrote:
> On (21/01/19 01:47), Matthew Wilcox wrote:
> [..]
> >
> > > 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.
>
> Oh, I see.
>
> > 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.
>
> I like the name. config dependent behaviour of %p wouldn't be new,
> well, to some extent, e.g. XFS does something similar (see below).
> I don't think Linus will be sold on this, however.
>
>
> fs/xfs/xfs_linux.h:
>
> /*
> * Starting in Linux 4.15, the %p (raw pointer value) printk modifier
> * prints a hashed version of the pointer to avoid leaking kernel
> * pointers into dmesg. If we're trying to debug the kernel we want the
> * raw values, so override this behavior as best we can.
> */
> #ifdef DEBUG
> # define PTR_FMT "%px"
> #else
> # define PTR_FMT "%p"
> #endif
>
> And then they just use it as
>
> xfs_alert(mp, "%s: bad inode magic number, dip = "ptr_fmt",
> dino bp = "ptr_fmt", ino = %ld",
> __func__, dip, bp, in_f->ilf_ino);
>
> -ss
Please no, this is effectively a toggle.
--
Kees Cook
next prev parent reply other threads:[~2021-01-19 19:52 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-16 22:09 [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps Timur Tabi
2021-01-16 22:09 ` [PATCH 1/2] [v2] lib/hexdump: introduce DUMP_PREFIX_UNHASHED for unhashed addresses Timur Tabi
2021-01-18 10:03 ` Andy Shevchenko
2021-01-18 15:57 ` Timur Tabi
2021-01-18 17:14 ` Andy Shevchenko
2021-01-18 17:53 ` Timur Tabi
2021-01-16 22:09 ` [PATCH 2/2] mm/page_poison: use unhashed address in hexdump for check_poison_mem() Timur Tabi
2021-01-18 18:26 ` [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps Matthew Wilcox
2021-01-18 19:03 ` Timur Tabi
2021-01-19 0:53 ` Sergey Senozhatsky
2021-01-19 1:47 ` Matthew Wilcox
2021-01-19 10:38 ` Sergey Senozhatsky
2021-01-19 19:45 ` Kees Cook [this message]
2021-01-26 16:47 ` Vlastimil Babka
2021-01-26 16:59 ` Timur Tabi
2021-01-26 17:14 ` Steven Rostedt
2021-01-26 17:14 ` Vlastimil Babka
2021-01-26 17:30 ` Timur Tabi
2021-01-26 17:39 ` Steven Rostedt
2021-01-26 17:40 ` Steven Rostedt
2021-01-26 19:23 ` John Ogness
2021-01-27 2:11 ` Sergey Senozhatsky
2021-01-27 3:22 ` Timur Tabi
2021-01-27 10:11 ` Petr Mladek
2021-01-27 10:38 ` Vlastimil Babka
2021-01-19 19:45 ` Kees Cook
2021-01-19 19:55 ` Timur Tabi
2021-01-19 20:10 ` Steven Rostedt
2021-01-19 20:49 ` Timur Tabi
2021-01-19 21:15 ` Steven Rostedt
2021-01-19 21:25 ` Timur Tabi
2021-01-20 9:19 ` Petr Mladek
2021-01-20 12:17 ` Matthew Wilcox
2021-01-20 19:39 ` Linus Torvalds
2021-01-19 20:18 ` Randy Dunlap
2021-01-20 20:28 ` Kees Cook
2021-01-19 2:30 ` Timur Tabi
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