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Date:   Sat, 17 Mar 2018 10:29:35 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To:     Petr Mladek <pmladek@suse.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Steven Rostedt <rostedt@goodmis.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
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On (03/16/18 09:55), Petr Mladek wrote:
[..]
> I am not sure if it is worth it. I think that we would catch 99% of
> problems by checking the first byte.
> 
> This patch was motivated by a code clean up rather than bug reports.

OK. Then I think we really need this "the patch is just good enough" line
in the commit message and a big comment in the source code.

Another idea (just an idea) - for some pointers we know the address range
we are going to access and can check the first and the last byte. E.g. for
UUID it's check_access(ptr) and check_access(ptr + len), and so on. Won't
work for string() in general case, tho.

	-ss