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Date: Wed, 22 Mar 2017 13:54:10 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Andy Lutomirski <luto@...capital.net>,
Thomas Garnier <thgarnie@...gle.com>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Dave Hansen <dave.hansen@...el.com>,
David Howells <dhowells@...hat.com>, Al Viro <viro@...iv.linux.org.uk>,
Arnd Bergmann <arnd@...db.de>,
René Nyffenegger <mail@...enyffenegger.ch>,
Andrew Morton <akpm@...ux-foundation.org>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
Ingo Molnar <mingo@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
Oleg Nesterov <oleg@...hat.com>,
Pavel Tikhomirov
<ptikhomirov@...tuozzo.com>,
Stephen Smalley <sds@...ho.nsa.gov>, Ingo Molnar <mingo@...hat.com>,
Andy Lutomirski <luto@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>,
Rik van Riel <riel@...hat.com>, Kees Cook <keescook@...omium.org>,
Josh Poimboeuf <jpoimboe@...hat.com>, Borislav Petkov <bp@...en8.de>,
Brian Gerst <brgerst@...il.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Russell King <linux@...linux.org.uk>,
Vladimir Murzin <vladimir.murzin@....com>,
Will Deacon
<will.deacon@....com>,
Catalin Marinas <catalin.marinas@....com>,
Mark Rutland <mark.rutland@....com>, James Morse <james.morse@....com>,
"linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Linux API <linux-api@...r.kernel.org>, X86 ML <x86@...nel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v4 1/4] syscalls: Restore address limit after a syscall
On 03/22/17 13:44, Andy Lutomirski wrote:
>
> While it's possible that silently papering over the bug is slightly
> faster than BUGging, it will allow bugs to continue to exist
> undetected.
>
It would also allow the test to be inlined (at least on architectures
which have a one-site implementation) and have only the failure case out
of line, with a __noreturn annotation (which allows it to be jumped to
rather than called, which is usually available as a conditional
operation whereas call often isn't.)
That is...
extern void __noreturn __pre_usermode_state_invalid(void);
static void verify_pre_usermode_state(void)
{
if (unlikely(!segment_eq(get_fs(), USER_DS))
__pre_usermode_state_invalid();
}
-hpa
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