Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752966AbbF3LG6 (ORCPT ); Tue, 30 Jun 2015 07:06:58 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:34462 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752783AbbF3LGv (ORCPT ); Tue, 30 Jun 2015 07:06:51 -0400 Date: Tue, 30 Jun 2015 13:06:46 +0200 From: Ingo Molnar To: Borislav Petkov Cc: Andy Lutomirski , x86@kernel.org, linux-kernel@vger.kernel.org, =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Rik van Riel , Oleg Nesterov , Denys Vlasenko , Kees Cook , Brian Gerst , paulmck@linux.vnet.ibm.com Subject: Re: [PATCH v4 02/17] x86/entry/64/compat: Fix bad fast syscall arg failure path Message-ID: <20150630110645.GB25988@gmail.com> References: <903010762c07a3d67df914fea2da84b52b0f8f1d.1435602481.git.luto@kernel.org> <20150630105855.GB23297@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150630105855.GB23297@pd.tnic> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1742 Lines: 45 * Borislav Petkov wrote: > On Mon, Jun 29, 2015 at 12:33:34PM -0700, Andy Lutomirski wrote: > > diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S > > index bb187a6a877c..efe0b1e499fa 100644 > > --- a/arch/x86/entry/entry_64_compat.S > > +++ b/arch/x86/entry/entry_64_compat.S > > @@ -425,8 +425,39 @@ cstar_tracesys: > > END(entry_SYSCALL_compat) > > > > ia32_badarg: > > - ASM_CLAC > > - movq $-EFAULT, RAX(%rsp) > > + /* > > + * So far, we've entered kernel mode, set AC, turned on IRQs, and > > + * saved C regs except r8-r11. We haven't done any of the other > > + * standard entry work, though. We want to bail, but we shouldn't > > + * treat this as a syscall entry since we don't even know what the > > + * args are. Instead, treat this as a non-syscall entry, finish > > + * the entry work, and immediately exit after setting AX = -EFAULT. > > + * > > + * We're really just being polite here. Killing the task outright > > + * would be a reasonable action, too. Given that the only valid > > + * way to have gotten here is through the vDSO, and we already know > > + * that the stack pointer is bad, the task isn't going to survive > > + * for long no matter what we do. > > You mean something like > > force_sig_info(SIGSEGV, &si, current); > > ? We should also emit a warning message, even if user-space installed a 'special' sigfault handler to hide such failures. (I'm looking at you systemd!) Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/