From patchwork Mon Jan 11 21:44:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tony Luck X-Patchwork-Id: 12011707 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 785F9C433E0 for ; Mon, 11 Jan 2021 21:45:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1181C22CAF for ; Mon, 11 Jan 2021 21:45:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1181C22CAF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 711428D0058; Mon, 11 Jan 2021 16:45:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6E7E78D0051; Mon, 11 Jan 2021 16:45:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5D6F78D0058; Mon, 11 Jan 2021 16:45:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0193.hostedemail.com [216.40.44.193]) by kanga.kvack.org (Postfix) with ESMTP id 3F08C8D0051 for ; Mon, 11 Jan 2021 16:45:19 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 044131EE6 for ; Mon, 11 Jan 2021 21:45:19 +0000 (UTC) X-FDA: 77694825558.08.maid65_3503bd127510 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id D57E11819E766 for ; Mon, 11 Jan 2021 21:45:18 +0000 (UTC) X-HE-Tag: maid65_3503bd127510 X-Filterd-Recvd-Size: 3005 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by imf22.hostedemail.com (Postfix) with ESMTP for ; Mon, 11 Jan 2021 21:45:16 +0000 (UTC) IronPort-SDR: Ytmx3DncrbAnN9D7ll+G3926bt7PxVFBurzNc97Yjpk5/PAOnXuG6EqXZq7NvolIn1Jccyl/Fk Ng5l12JJqzlA== X-IronPort-AV: E=McAfee;i="6000,8403,9861"; a="157718794" X-IronPort-AV: E=Sophos;i="5.79,339,1602572400"; d="scan'208";a="157718794" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2021 13:45:09 -0800 IronPort-SDR: +hZpGNm/k1XCMrPo4g89/aNf7U2+ZmNAXdUEFb5sHxdr4/ePzBAjecP6x/wx3X/nPg3xc+P4vb GyWVQYoOAztw== X-IronPort-AV: E=Sophos;i="5.79,339,1602572400"; d="scan'208";a="352760874" Received: from agluck-desk2.sc.intel.com ([10.3.52.68]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2021 13:45:08 -0800 From: Tony Luck To: Borislav Petkov Cc: Tony Luck , x86@kernel.org, Andrew Morton , Peter Zijlstra , Darren Hart , Andy Lutomirski , linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 3/3] futex, x86/mce: Avoid double machine checks Date: Mon, 11 Jan 2021 13:44:52 -0800 Message-Id: <20210111214452.1826-4-tony.luck@intel.com> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20210111214452.1826-1-tony.luck@intel.com> References: <20210108222251.14391-1-tony.luck@intel.com> <20210111214452.1826-1-tony.luck@intel.com> MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: futex_wait_setup() first tries to read the user value with page faults disabled (because it holds a lock, and so cannot sleep). If that read fails it drops the lock and tries again. But there are now two reasons why the user space read can fail. Either: 1) legacy case of a page fault, in which case it is reasonable to retry 2) machine check on the user address, bad idea to re-read Check for the ENXIO return code from the first get_user() call and immediately return an error without re-reading the futex. Signed-off-by: Tony Luck --- kernel/futex.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/futex.c b/kernel/futex.c index c47d1015d759..b11166712a9f 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -723,7 +723,7 @@ static int get_futex_value_locked(u32 *dest, u32 __user *from) ret = __get_user(*dest, from); pagefault_enable(); - return ret ? -EFAULT : 0; + return (ret == -ENXIO) ? ret : ret ? -EFAULT : 0; } @@ -2658,6 +2658,9 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, if (ret) { queue_unlock(*hb); + if (ret == -ENXIO) + return ret; + ret = get_user(uval, uaddr); if (ret) return ret;