linux-kernel - Re: [PATCH 4/5] x86, boot: Make memcpy handle overlaps

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Message-ID: <20160422075610.GD7352@gmail.com>
Date:	Fri, 22 Apr 2016 09:56:11 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	Yinghai Lu <yinghai@...nel.org>, Baoquan He <bhe@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	"H.J. Lu" <hjl.tools@...il.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Borislav Petkov <bp@...e.de>,
	Andy Lutomirski <luto@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] x86, boot: Make memcpy handle overlaps

* Kees Cook <keescook@...omium.org> wrote:

> Two uses of memcpy (screen scrolling and ELF parsing) were handling
> overlapping memory areas. While there were no explicitly noticed bugs
> here (yet), it is best to fix this so that the copying will always be
> safe.
> 
> Instead of making a new memmove function that might collide with other
> memmove definitions in the decompressors, this just makes the compressed
> boot's copy of memcpy overlap safe.

Btw., I changed all mentions of function calls to include a '()', i.e.:

 Subject: x86/boot: Make memcpy() handle overlaps
 From: Kees Cook <keescook@...omium.org>
 Date: Wed, 20 Apr 2016 13:55:45 -0700

 Two uses of memcpy() (screen scrolling and ELF parsing) were handling
 overlapping memory areas. While there were no explicitly noticed bugs
 here (yet), it is best to fix this so that the copying will always be
 safe.

 Instead of making a new memmove() function that might collide with other
 memmove() definitions in the decompressors, this just makes the compressed
 boot code's copy of memcpy() overlap-safe.

Please try to do this in future changelogs and patch titles, all references to 
function calls should use parentheses, and all references to variables or 
parameters should be escaped with '...' when it's not abundantly clear what they 
are - this makes for much easier reading.

So just to mention an extreme (made up) example, which of these two commit titles 
is less confusing to read:

  Change out parameter of function to buffer to avoid confusion

or:

  Change 'out' parameter of function() to 'buffer' to avoid confusion

?

I know which one I'd pick! ;-)

Thanks,

	Ingo