From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF371C2BA1E for ; Mon, 15 Mar 2021 14:10:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7C30464E33 for ; Mon, 15 Mar 2021 14:10:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234843AbhCOOJx (ORCPT ); Mon, 15 Mar 2021 10:09:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:52482 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234593AbhCOOE1 (ORCPT ); Mon, 15 Mar 2021 10:04:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 15F9D64F19; Mon, 15 Mar 2021 14:04:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1615817062; bh=PfnVeY2t2Sio7VEsOHhFYgCN4N3QZ/B7btLz1CFDubw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SdcFem8KLun58QauXruFu4aWnhvg8j6owSlML1TcmI4o1hlhgvMI1LCHPbXARScSw vwDv7YJ3xdY8UFV5oPNcGvDDZLeyNeCAJlW+tMK2j+h7gxIB3lCoN4iL9Xn9C8jEhP cMojwTG6EpqfxX3QSzjntb0fMzxvBk5s5iJNWRYs= From: gregkh@linuxfoundation.org To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Ivan Babrou , Josh Poimboeuf , "Peter Zijlstra (Intel)" , Borislav Petkov , "Steven Rostedt (VMware)" , stable@kernel.org Subject: [PATCH 5.10 269/290] x86/unwind/orc: Disable KASAN checking in the ORC unwinder, part 2 Date: Mon, 15 Mar 2021 14:56:02 +0100 Message-Id: <20210315135551.107131583@linuxfoundation.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210315135541.921894249@linuxfoundation.org> References: <20210315135541.921894249@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Greg Kroah-Hartman From: Josh Poimboeuf commit e504e74cc3a2c092b05577ce3e8e013fae7d94e6 upstream. KASAN reserves "redzone" areas between stack frames in order to detect stack overruns. A read or write to such an area triggers a KASAN "stack-out-of-bounds" BUG. Normally, the ORC unwinder stays in-bounds and doesn't access the redzone. But sometimes it can't find ORC metadata for a given instruction. This can happen for code which is missing ORC metadata, or for generated code. In such cases, the unwinder attempts to fall back to frame pointers, as a best-effort type thing. This fallback often works, but when it doesn't, the unwinder can get confused and go off into the weeds into the KASAN redzone, triggering the aforementioned KASAN BUG. But in this case, the unwinder's confusion is actually harmless and working as designed. It already has checks in place to prevent off-stack accesses, but those checks get short-circuited by the KASAN BUG. And a BUG is a lot more disruptive than a harmless unwinder warning. Disable the KASAN checks by using READ_ONCE_NOCHECK() for all stack accesses. This finishes the job started by commit 881125bfe65b ("x86/unwind: Disable KASAN checking in the ORC unwinder"), which only partially fixed the issue. Fixes: ee9f8fce9964 ("x86/unwind: Add the ORC unwinder") Reported-by: Ivan Babrou Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Steven Rostedt (VMware) Tested-by: Ivan Babrou Cc: stable@kernel.org Link: https://lkml.kernel.org/r/9583327904ebbbeda399eca9c56d6c7085ac20fe.1612534649.git.jpoimboe@redhat.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/unwind_orc.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- a/arch/x86/kernel/unwind_orc.c +++ b/arch/x86/kernel/unwind_orc.c @@ -367,8 +367,8 @@ static bool deref_stack_regs(struct unwi if (!stack_access_ok(state, addr, sizeof(struct pt_regs))) return false; - *ip = regs->ip; - *sp = regs->sp; + *ip = READ_ONCE_NOCHECK(regs->ip); + *sp = READ_ONCE_NOCHECK(regs->sp); return true; } @@ -380,8 +380,8 @@ static bool deref_stack_iret_regs(struct if (!stack_access_ok(state, addr, IRET_FRAME_SIZE)) return false; - *ip = regs->ip; - *sp = regs->sp; + *ip = READ_ONCE_NOCHECK(regs->ip); + *sp = READ_ONCE_NOCHECK(regs->sp); return true; } @@ -402,12 +402,12 @@ static bool get_reg(struct unwind_state return false; if (state->full_regs) { - *val = ((unsigned long *)state->regs)[reg]; + *val = READ_ONCE_NOCHECK(((unsigned long *)state->regs)[reg]); return true; } if (state->prev_regs) { - *val = ((unsigned long *)state->prev_regs)[reg]; + *val = READ_ONCE_NOCHECK(((unsigned long *)state->prev_regs)[reg]); return true; }