From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: [PATCH v4 10/29] x86/die: Don't try to recover from an OOPS on a non-default stack Date: Sat, 2 Jul 2016 19:24:41 +0200 Message-ID: <20160702172441.GA22748@pd.tnic> References: <37ac7589ff0ea147e8a21cda5eb84d3af1f6cd60.1466974736.git.luto@kernel.org> Reply-To: kernel-hardening@lists.openwall.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Content-Disposition: inline In-Reply-To: <37ac7589ff0ea147e8a21cda5eb84d3af1f6cd60.1466974736.git.luto@kernel.org> To: Andy Lutomirski Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Nadav Amit , Kees Cook , Brian Gerst , "kernel-hardening@lists.openwall.com" , Linus Torvalds , Josh Poimboeuf , Jann Horn , Heiko Carstens List-Id: linux-arch.vger.kernel.org On Sun, Jun 26, 2016 at 02:55:32PM -0700, Andy Lutomirski wrote: > It's not going to work, because the scheduler will explode if we try > to schedule when running on an IST stack or similar. > > This will matter when we let kernel stack overflows (which are #DF) > call die(). > > Signed-off-by: Andy Lutomirski > --- > arch/x86/kernel/dumpstack.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c > index ef8017ca5ba9..352f022cfd5b 100644 > --- a/arch/x86/kernel/dumpstack.c > +++ b/arch/x86/kernel/dumpstack.c > @@ -245,6 +245,9 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr) > return; > if (in_interrupt()) > panic("Fatal exception in interrupt"); > + if (((current_stack_pointer() ^ (current_top_of_stack() - 1)) > + & ~(THREAD_SIZE - 1)) != 0) Ugh, that's hard to parse. You could remove the "!= 0" at least to shorten it a bit and have one less braces level. Or maybe even do something like that to make it a bit more readable: if ((current_stack_pointer() ^ (current_top_of_stack() - 1)) & ~(THREAD_SIZE - 1)) panic("Fatal exception on non-default stack"); Meh. > + panic("Fatal exception on special stack"); "Fatal exception on non-default stack" maybe? -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.skyhub.de ([78.46.96.112]:38592 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752246AbcGBRZL (ORCPT ); Sat, 2 Jul 2016 13:25:11 -0400 Date: Sat, 2 Jul 2016 19:24:41 +0200 From: Borislav Petkov Subject: Re: [PATCH v4 10/29] x86/die: Don't try to recover from an OOPS on a non-default stack Message-ID: <20160702172441.GA22748@pd.tnic> References: <37ac7589ff0ea147e8a21cda5eb84d3af1f6cd60.1466974736.git.luto@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <37ac7589ff0ea147e8a21cda5eb84d3af1f6cd60.1466974736.git.luto@kernel.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Andy Lutomirski Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, Nadav Amit , Kees Cook , Brian Gerst , "kernel-hardening@lists.openwall.com" , Linus Torvalds , Josh Poimboeuf , Jann Horn , Heiko Carstens Message-ID: <20160702172441.ZQwV6Wbcldp8THfZ3nAZFi4RPIrXr7JHBRBt6R1skyY@z> On Sun, Jun 26, 2016 at 02:55:32PM -0700, Andy Lutomirski wrote: > It's not going to work, because the scheduler will explode if we try > to schedule when running on an IST stack or similar. > > This will matter when we let kernel stack overflows (which are #DF) > call die(). > > Signed-off-by: Andy Lutomirski > --- > arch/x86/kernel/dumpstack.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c > index ef8017ca5ba9..352f022cfd5b 100644 > --- a/arch/x86/kernel/dumpstack.c > +++ b/arch/x86/kernel/dumpstack.c > @@ -245,6 +245,9 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr) > return; > if (in_interrupt()) > panic("Fatal exception in interrupt"); > + if (((current_stack_pointer() ^ (current_top_of_stack() - 1)) > + & ~(THREAD_SIZE - 1)) != 0) Ugh, that's hard to parse. You could remove the "!= 0" at least to shorten it a bit and have one less braces level. Or maybe even do something like that to make it a bit more readable: if ((current_stack_pointer() ^ (current_top_of_stack() - 1)) & ~(THREAD_SIZE - 1)) panic("Fatal exception on non-default stack"); Meh. > + panic("Fatal exception on special stack"); "Fatal exception on non-default stack" maybe? -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.