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=-20.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 27C5DC4332B for ; Thu, 4 Mar 2021 08:53:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1273E64F20 for ; Thu, 4 Mar 2021 08:53:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236898AbhCDIwr (ORCPT ); Thu, 4 Mar 2021 03:52:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46548 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236843AbhCDIwU (ORCPT ); Thu, 4 Mar 2021 03:52:20 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 84C73C06175F; Thu, 4 Mar 2021 00:51:40 -0800 (PST) Date: Thu, 04 Mar 2021 08:51:35 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1614847896; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kF5T/oM0xIFrRq6MAf0rXEWInAZVAeVJD5ZWqjmSnSA=; b=noU/dIAft1w9lYMbxfIwlYyNqNwY3KY4Vgpe6J/cfwgqElVNp1ZPv+U1b4Gyn4vy0ce2AO snP1jWZxRK7zhmv2nPi1/lwVHv/VL9Cy75qj18lw4iWdhRzTCToUueqNt5/MQ9OlW3mjT8 80/4vqSq0Xdgi7Si9XeghWQooWl8WSKMj3FpSfRLdZ6HOvbPp0DprcllWkTdpjHaQ2ttix TrxduChJsjqvIjNwDMLTsnKfj3zaaAlmWLZAwCrS5BkDehnaaqSroK5uxGQFMuwzdvAsRb c8fB1ePdMpC5sOARQs/NKGoLB1Ftt0Se/D5LFnePWd+03dUlr8c51v9duZjfDg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1614847896; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kF5T/oM0xIFrRq6MAf0rXEWInAZVAeVJD5ZWqjmSnSA=; b=4Uz+1D08Y260zHulD/u4UBsOXYUKU5260jxXEulz58QjxsSme4bXljG/KEO5uMnfJLJ+CW rzsmSsT/HxW5HVCQ== From: "tip-bot2 for Josh Poimboeuf" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/urgent] x86/unwind/orc: Disable KASAN checking in the ORC unwinder, part 2 Cc: Ivan Babrou , Josh Poimboeuf , "Peter Zijlstra (Intel)" , "Steven Rostedt (VMware)" , stable@kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <9583327904ebbbeda399eca9c56d6c7085ac20fe.1612534649.git.jpoimboe@redhat.com> References: <9583327904ebbbeda399eca9c56d6c7085ac20fe.1612534649.git.jpoimboe@redhat.com> MIME-Version: 1.0 Message-ID: <161484789559.398.7368272714633477349.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/urgent branch of tip: Commit-ID: 38b6eb474ed2df3d159396c3d4312c8a7b2d5196 Gitweb: https://git.kernel.org/tip/38b6eb474ed2df3d159396c3d4312c8a7b2d5196 Author: Josh Poimboeuf AuthorDate: Fri, 05 Feb 2021 08:24:02 -06:00 Committer: Peter Zijlstra CommitterDate: Wed, 03 Mar 2021 16:56:29 +01:00 x86/unwind/orc: Disable KASAN checking in the ORC unwinder, part 2 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) 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 --- arch/x86/kernel/unwind_orc.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c index 2a1d47f..1bcc14c 100644 --- a/arch/x86/kernel/unwind_orc.c +++ b/arch/x86/kernel/unwind_orc.c @@ -367,8 +367,8 @@ static bool deref_stack_regs(struct unwind_state *state, unsigned long addr, 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 unwind_state *state, unsigned long addr 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 *state, unsigned int reg_off, 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; }