linux-kernel - Re: [PATCH v4] x86/boot: Warn on future overlapping memcpy() use

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Date:	Fri, 29 Apr 2016 09:20:02 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	Lasse Collin <lasse.collin@...aani.org>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>, Baoquan He <bhe@...hat.com>,
	Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH v4] x86/boot: Warn on future overlapping memcpy() use


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

> On Thu, Apr 28, 2016 at 11:43 PM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Kees Cook <keescook@...omium.org> wrote:
> >
> >> If an overlapping memcpy() is ever attempted, we should at least report
> >> it, in case it might lead to problems, so it could be changed to a
> >> memmove() call instead.
> >>
> >> Suggested-by: Ingo Molnar <mingo@...nel.org>
> >> Signed-off-by: Kees Cook <keescook@...omium.org>
> >> ---
> >> v4:
> >> - use __memcpy not memcpy since we've already done the check.
> >> v3:
> >> - call memmove in addition to doing the warning
> >> v2:
> >> - warn about overlapping region
> >> ---
> >>  arch/x86/boot/compressed/string.c | 16 +++++++++++++---
> >>  1 file changed, 13 insertions(+), 3 deletions(-)
> >
> > Applied, thanks Kees!
> >
> > Btw., can we now also remove the memmove() hack from lib/decompress_unxz.c?
> 
> I'll let Lasse answer for sure, but I don't think so. The original commit says:
> 
>     The XZ decompressor needs memmove(), memeq() (memcmp() == 0), and
>     memzero() (memset(ptr, 0, size)), which aren't available in all
>     arch-specific pre-boot environments.  I'm including simple versions in
>     decompress_unxz.c, but a cleaner solution would naturally be nicer.

I see, so non-x86 architectures might not have the proper runtime environment 
implemented, right?

Fair enough!

Thanks,

	Ingo