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Date: Thu, 11 May 2017 13:22:34 +0200
From: Borislav Petkov <bp@...en8.de>
To: Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>
Cc: Christoph Hellwig <hch@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>,
	Greg KH <greg@...ah.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	Dave Hansen <dave.hansen@...el.com>,
	"H . Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-s390 <linux-s390@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Russell King <linux@...linux.org.uk>,
	Will Deacon <will.deacon@....com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	René Nyffenegger <mail@...enyffenegger.ch>,
	Catalin Marinas <catalin.marinas@....com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	Brian Gerst <brgerst@...il.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	Linux API <linux-api@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>, James Morse <james.morse@....com>,
	"Eric W . Biederman" <ebiederm@...ssion.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Garnier <thgarnie@...gle.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: Re: [PATCH v9 1/4] syscalls: Verify address
 limit before returning to user-mode

On Tue, May 09, 2017 at 04:31:00PM -0700, Kees Cook wrote:
> > I don't like silent fixups.  If we want to do this, we should BUG or
> > at least WARN, not just change the addr limit.  But I'm also not
> > convinced it's indicative of an actual bug here.
> 
> Nothing should enter that function with KERNEL_DS set, right?
> 
> BUG_ON(get_fs() != USER_DS);

We're feeling triggerhappy, aren't we? A nice juicy WARN-splat along
with a fixup looks much better than killing the box, to me.

-- 
Regards/Gruss,
    Boris.

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