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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9220EC4332F for ; Thu, 3 Nov 2022 13:45:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230526AbiKCNpo (ORCPT ); Thu, 3 Nov 2022 09:45:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46238 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229643AbiKCNpk (ORCPT ); Thu, 3 Nov 2022 09:45:40 -0400 Received: from mail-ed1-x549.google.com (mail-ed1-x549.google.com [IPv6:2a00:1450:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25F1EF50 for ; Thu, 3 Nov 2022 06:45:40 -0700 (PDT) Received: by mail-ed1-x549.google.com with SMTP id l18-20020a056402255200b004633509768bso1403470edb.12 for ; Thu, 03 Nov 2022 06:45:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=ScuUET3Jx3790WWtzDciWGjRGXPi9X8ISFOvBcfPIsI=; b=leCGMG1Ihb72GuqEhvKiIBXP3svrLi4GzMCcHOGP9PM8igal8vM5W4lXCqnNucSw3P 1fnQ15L2ZK8WgXHhy3OiPjE01iUPYRYjn+HLa1puFmYg6oh4P8+TsU59MFP97mWSj9Tp /GKp7HOeM/hBv8kUjeXHmP7yGCPjf5B8kOAo47zvM3+0u2Om3tQyaR9nGEpB2MOY4Aqj Y52eQAHsh/vMHHfCqhKOhQy4lGBB+wvxc9rt8N02K44QPooSfTBlbkqMBHldPPxcCiIP LS9pz4lZ2ruUA+NsjYpnhDCoLsQW3eMQvtR8LhsOJPoSnCydWfm6Zg1Hgi5CiuaqUFhQ mYkw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=ScuUET3Jx3790WWtzDciWGjRGXPi9X8ISFOvBcfPIsI=; b=r/65IbRtuYRA62SZH4/SjMHDHyCO1rT9CY8lv6j340ksAYhJDv5SgzWrb5QwDkEKKv 2ajteyZpKYrNoLub9c56UIaRoKzGLLFI5+EWrOU2SKcWksuyj9LzYY7rSFc8E90VZjij Y5AKx2bxwi606BfzRiudFhC+Hd691NIg2GpREGOtDBOJZznpF2MtE4NNkIbUvdxcwBHk dsjg/3qmfIf+oWUDA5o/JwalqfAlEOwJJqkoUKSVAQig3/V3s76uelBM0yT/01TE3qIH I2d7JJUFGxMCJS3PyUfmI0+i0TOpHyN7MspYEJ/SPOSQ2exZU19MSYSbcpKjlM8k0TSG 9L0Q== X-Gm-Message-State: ACrzQf1yOD+kVa2WA1OQsX+g0o2ErDEY3EARFV9GmHAV48VtF+IyBr73 CiIeyvYTcRhwTK3EiEFzsgJ41z+IGbo= X-Google-Smtp-Source: AMsMyM5txHoDUQHV74JbL/I6drhqJzAVd4b0cSj6OCCI9DN1HmElG8LQngrwgUKWVyAIdwt42FAiHVc9R6A= X-Received: from glider.muc.corp.google.com ([2a00:79e0:9c:201:f99b:157d:615b:bbd8]) (user=glider job=sendgmr) by 2002:a17:906:7d8c:b0:7ae:159d:1146 with SMTP id v12-20020a1709067d8c00b007ae159d1146mr3887934ejo.528.1667483138558; Thu, 03 Nov 2022 06:45:38 -0700 (PDT) Date: Thu, 3 Nov 2022 14:45:15 +0100 Mime-Version: 1.0 X-Mailer: git-send-email 2.38.1.273.g43a17bfeac-goog Message-ID: <20221103134515.1934867-1-glider@google.com> Subject: [PATCH v2] x86/traps: avoid KMSAN bugs originating from handle_bug() From: Alexander Potapenko To: glider@google.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Borislav Petkov , Dave Hansen , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , x86@kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is a case in exc_invalid_op handler that is executed outside the irqentry_enter()/irqentry_exit() region when an UD2 instruction is used to encode a call to __warn(). In that case the `struct pt_regs` passed to the interrupt handler is never unpoisoned by KMSAN (this is normally done in irqentry_enter()), which leads to false positives inside handle_bug(). Use kmsan_unpoison_entry_regs() to explicitly unpoison those registers before using them. Cc: Andrew Morton Cc: Borislav Petkov Cc: Dave Hansen Cc: Ingo Molnar Cc: Peter Zijlstra (Intel) Cc: Thomas Gleixner Cc: x86@kernel.org Signed-off-by: Alexander Potapenko --- v2: - move the call to kmsan_unpoison_entry_regs() after the instrumentation_begin(), as suggested by Peter Zijlstra --- arch/x86/kernel/traps.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 178015a820f08..66701b4d99acd 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -308,6 +309,13 @@ static noinstr bool handle_bug(struct pt_regs *regs) * All lies, just get the WARN/BUG out. */ instrumentation_begin(); + + /* + * Normally @regs are unpoisoned by irqentry_enter(), but handle_bug() + * is a rare case that uses @regs without passing them to + * irqentry_enter(). + */ + kmsan_unpoison_entry_regs(regs); /* * Since we're emulating a CALL with exceptions, restore the interrupt * state to what it was at the exception site. -- 2.38.1.273.g43a17bfeac-goog