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From: Steven Rostedt <rostedt@goodmis.org>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	"Tobin C . Harding" <me@tobin.cc>, Joe Perches <joe@perches.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Michal Hocko <mhocko@suse.cz>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [PATCH v3] vsprintf: Prevent crash when dereferencing invalid pointers
Date: Fri, 16 Mar 2018 10:32:07 -0400	[thread overview]
Message-ID: <20180316103207.47d3ece7@gandalf.local.home> (raw)
In-Reply-To: <20180316085556.t3j65zyuyjzro3n3@pathway.suse.cz>

On Fri, 16 Mar 2018 09:55:56 +0100
Petr Mladek <pmladek@suse.com> wrote:

> I am not sure if it is worth it. I think that we would catch 99% of
> problems by checking the first byte.

Then it should be commented as such. Something like:

 /*
  * This is not a fool-proof test. 99.9% of the time that this will
  * fault is due to a bad pointer, not one that crosses into bad memory.
  * Just test the address to make sure it doesn't fault due to a poorly
  * added printk during debugging.
  */

> 
> This patch was motivated by a code clean up rather than bug reports.
> The original patch removed two more strict checks and kept only
> the check for pure NULL. I suggested that it was the wrong way to
> go...
> 
> I do not want to go suddenly to the other extreme. I suggest to start
> with simple check for the first byte and see how often it helps
> in the real life. We could always extend it later.

Fair enough. If this is just code clean up, then sure, we don't need to
cover all cases. But it should definitely be commented about why this
is added, and if in the future we really do want this to be more
robust, then we can extend it.

-- Steve

  reply	other threads:[~2018-03-16 14:32 UTC|newest]

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-16 21:07 [PATCH v2 1/9] lib/test_printf: Mark big constant with ULL Andy Shevchenko
2018-02-16 21:07 ` [PATCH v2 2/9] lib/vsprintf: Make dec_spec global Andy Shevchenko
2018-04-11  9:44   ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 3/9] lib/vsprintf: Make strspec global Andy Shevchenko
2018-04-11  9:44   ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 4/9] lib/vsprintf: Make flag_spec global Andy Shevchenko
2018-04-11  9:45   ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 5/9] lib/vsprintf: Move pointer_string() upper Andy Shevchenko
2018-04-11  9:45   ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 6/9] lib/vsprintf: Deduplicate pointer_string() Andy Shevchenko
2018-04-11  9:46   ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 7/9] lib/vsprintf: Replace space with '_' before crng is ready Andy Shevchenko
2018-02-20  2:57   ` [此邮件可能存在风险] " Yang, Shunyong
2018-04-11  9:47   ` Petr Mladek
2018-02-16 21:07 ` [PATCH v2 8/9] lib/vsprintf: Remove useless NULL checks Andy Shevchenko
2018-02-27 15:50   ` Petr Mladek
2018-02-27 17:35     ` Andy Shevchenko
2018-02-28 10:04       ` Petr Mladek
2018-02-28 10:42         ` Andy Shevchenko
2018-03-02 12:51           ` Petr Mladek
2018-03-02 12:53             ` [PATCH] vsprintf: Make "null" pointer dereference more robust Petr Mladek
2018-03-02 14:17               ` Andy Shevchenko
2018-03-05 14:53                 ` Petr Mladek
2018-03-29 15:13                 ` Petr Mladek
2018-03-29 16:11                   ` Joe Perches
2018-03-05 15:16               ` Rasmus Villemoes
2018-03-05 15:25                 ` Andy Shevchenko
2018-03-06  9:25                 ` Petr Mladek
2018-03-06  9:56                   ` Andy Shevchenko
2018-03-07 15:52                     ` Petr Mladek
2018-03-07 18:18                       ` Andy Shevchenko
2018-03-07 18:34                       ` Linus Torvalds
2018-03-08 14:18                         ` Petr Mladek
2018-03-08 16:45                           ` Linus Torvalds
2018-03-08 17:26                             ` Linus Torvalds
2018-03-09 15:01                               ` Petr Mladek
2018-03-09 19:05                                 ` Linus Torvalds
2018-03-14 14:09                                   ` [PATCH v3] vsprintf: Prevent crash when dereferencing invalid pointers Petr Mladek
2018-03-14 22:12                                     ` Rasmus Villemoes
2018-03-15 15:07                                       ` Petr Mladek
2018-03-15 17:07                                         ` Steven Rostedt
2018-03-15 17:06                                       ` Steven Rostedt
2018-03-15  0:57                                     ` Sergey Senozhatsky
2018-03-15  7:58                                     ` Sergey Senozhatsky
2018-03-15  8:03                                       ` Sergey Senozhatsky
2018-03-15 17:01                                         ` Steven Rostedt
2018-03-16  1:18                                           ` Sergey Senozhatsky
2018-03-16  1:35                                             ` Linus Torvalds
2018-03-16  5:53                                               ` Sergey Senozhatsky
2018-03-16  8:55                                                 ` Petr Mladek
2018-03-16 14:32                                                   ` Steven Rostedt [this message]
2018-03-17  1:29                                                   ` Sergey Senozhatsky
2018-03-15 13:07                                       ` Andy Shevchenko
2018-03-15 13:09                                     ` Andy Shevchenko
2018-03-15 15:26                                       ` Petr Mladek
2018-03-16 18:19                                         ` Andy Shevchenko
2018-03-29 14:53                                           ` Petr Mladek
2018-04-02 14:15                                             ` Andy Shevchenko
2018-04-03  1:12                                               ` Sergey Senozhatsky
2018-04-03 11:52                                                 ` Petr Mladek
2018-04-03 11:56                                                   ` Andy Shevchenko
2018-04-03 13:57                                                   ` Sergey Senozhatsky
2018-04-03 11:46                                               ` Petr Mladek
2018-04-03 11:54                                                 ` Andy Shevchenko
2018-04-03 13:13                                                   ` Petr Mladek
2018-04-03 13:40                                                     ` Andy Shevchenko
2018-04-03 14:50                                                       ` Petr Mladek
2018-03-15 14:48                                     ` kbuild test robot
2018-03-15 20:26                                     ` kbuild test robot
2018-03-06 18:11                   ` [PATCH 1/2] vsprintf: distinguish between (null), (err) and (invalid) pointer derefs Adam Borowski
2018-03-06 18:11                     ` [PATCH 2/2] vsprintf: don't dereference pointers to the first or last page Adam Borowski
2018-03-07 13:22                       ` Andy Shevchenko
2018-03-07 13:17                     ` [PATCH 1/2] vsprintf: distinguish between (null), (err) and (invalid) pointer derefs Andy Shevchenko
2018-03-07 13:42                       ` Adam Borowski
2018-03-07 13:29                     ` Andy Shevchenko
2018-03-02 14:15             ` [PATCH v2 8/9] lib/vsprintf: Remove useless NULL checks Andy Shevchenko
2018-03-05 14:57               ` Petr Mladek
2018-02-28 10:44         ` Andy Shevchenko
2018-03-01 14:56         ` Andy Shevchenko
2018-02-16 21:07 ` [PATCH v2 9/9] lib/vsprintf: Mark expected switch fall-through Andy Shevchenko
2018-04-11  9:47   ` Petr Mladek
2018-02-18 12:58 ` [PATCH v2 1/9] lib/test_printf: Mark big constant with ULL Luc Van Oostenryck
2018-02-18 14:20   ` Andy Shevchenko
2018-02-19 15:24   ` Andy Shevchenko
2018-04-11  9:41     ` Petr Mladek
2018-02-18 21:52 ` Tobin C. Harding
2018-02-18 23:55   ` Andy Shevchenko

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