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=-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=unavailable 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 4ADD2C433E6 for ; Mon, 11 Jan 2021 21:46:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA45F22CB8 for ; Mon, 11 Jan 2021 21:46:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388293AbhAKVqa (ORCPT ); Mon, 11 Jan 2021 16:46:30 -0500 Received: from mga14.intel.com ([192.55.52.115]:20926 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731135AbhAKVq3 (ORCPT ); Mon, 11 Jan 2021 16:46:29 -0500 IronPort-SDR: +2t+Mdtmtl6g2dk7YF2UYUJ8jJN6w4gl6ZCntod3VCageBFm0FUumbmb2OfQQLVaqgHVaW7slc Qzpqh8swNDAA== X-IronPort-AV: E=McAfee;i="6000,8403,9861"; a="177166211" X-IronPort-AV: E=Sophos;i="5.79,339,1602572400"; d="scan'208";a="177166211" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2021 13:45:08 -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 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; -- 2.21.1