From patchwork Mon Apr 9 00:26:43 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sasha Levin X-Patchwork-Id: 132951 Delivered-To: patch@linaro.org Received: by 10.46.84.29 with SMTP id i29csp647111ljb; Sun, 8 Apr 2018 17:35:09 -0700 (PDT) X-Google-Smtp-Source: AIpwx4+/vkIj+PQKIWd3ZuZ6CXVtYR5rwbsTWdYEqM5pk/9Ox5WpcQ/kYyn4mfPiKWpm7Vi0c6fn X-Received: by 10.99.3.144 with SMTP id 138mr23806110pgd.364.1523234109154; Sun, 08 Apr 2018 17:35:09 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1523234109; cv=none; d=google.com; s=arc-20160816; b=MQqk+kapZAvYDcSixfxyZisKMd1TQ2p2HUbcsK1ezZb1SAoPvf0kjjg9xSamAr2Su7 tDP2PQSJTQSUqfF8LfqYQmvGZNNwbWJIkIumCYwJLz7Ft9A+7aWaFVcCL5euW3lyEvB0 odZH4BmzMnLWo8L+rAxuw6ZhvaeC9PXqHc6T7oQxBDgLDBYDr22HfxyueTRqA6UJluVG 6KE/ylFfSX56AEmlXuK4GLnjk6XublVZteFN7IZCUwyO4c56sShqRzxKperjRXfD4P/R gRIJZ/lLtXTQltrwG8XDVFmXaS0fGXUX8E1Yg7QHlw1HXiA77JnXmTFiS/cT7OxKd51l h0Ng== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:mime-version:content-transfer-encoding :spamdiagnosticmetadata:spamdiagnosticoutput:content-language :accept-language:in-reply-to:references:message-id:date:thread-index :thread-topic:subject:cc:to:from:dkim-signature :arc-authentication-results; bh=xv+MzhbRqk6xoDlsTW4eQIjUoBlwxhsDdVI7cKoOnXw=; b=tVpvqODcyUj538h+S+5kcI5O4qbBxn9GFCrpeRNjVcSQtx6cbdVi7dPBUmApdHL+cQ k+AUU6xauDL/AcoVgUu6cyOqi+VkOqxCNXbZhLuGqUZkmgDNNWz/gZDGekYQM3YSRV18 Nh+/t/Juf3YoFsQjjwqJIY3jLymY9U+NZHxBFM6jVwodlccZyGv3Rmp6nVUcw1LnWj2p s+0xaQJHqAlTibaz3NXw/MTozwrl9JfKlR2vb4lsEkOIjR1qimYwhjVGtGIkDIaRebkE Bnu1Jb2st2uGHSwcmm6VfWgPxd5igl1MXKbVMlSN3mqiJITo6bDg9rQdlNBpr0H8+i8A 8P5Q== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@microsoft.com header.s=selector1 header.b=F83qCKav; spf=pass (google.com: best guess record for domain of stable-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=stable-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=microsoft.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. 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Sun, 8 Apr 2018 20:34:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=xv+MzhbRqk6xoDlsTW4eQIjUoBlwxhsDdVI7cKoOnXw=; b=F83qCKavyxGobMroE6msIaKQwWGIYRrbt767y76fe0MJPOtYpZv02HkUcgTPiWxmjmi7tlqYNsfxhRn3pJ4kWTyuLELQLC1B+Z7sP1J8BYlpzlM2M+ARMOuwTuA70T2VoWz8MB/NhRQSysIDsOJx7YHWJh+26f1i4lmTjO1B8uk= Received: from DM5PR2101MB1032.namprd21.prod.outlook.com (52.132.128.13) by DM5PR2101MB0806.namprd21.prod.outlook.com (10.167.107.156) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.696.3; Mon, 9 Apr 2018 00:34:47 +0000 Received: from DM5PR2101MB1032.namprd21.prod.outlook.com ([fe80::8109:aef0:a777:7059]) by DM5PR2101MB1032.namprd21.prod.outlook.com ([fe80::8109:aef0:a777:7059%2]) with mapi id 15.20.0696.003; Mon, 9 Apr 2018 00:34:47 +0000 From: Sasha Levin To: "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" CC: Will Deacon , Linus Torvalds , Thomas Gleixner , Ingo Molnar , Sasha Levin Subject: [PATCH AUTOSEL for 4.9 290/293] locking/qspinlock: Ensure node->count is updated before initialising node Thread-Topic: [PATCH AUTOSEL for 4.9 290/293] locking/qspinlock: Ensure node->count is updated before initialising node Thread-Index: AQHTz5lv3gsVWtfZGUasLrStRynHag== Date: Mon, 9 Apr 2018 00:26:43 +0000 Message-ID: <20180409002239.163177-290-alexander.levin@microsoft.com> References: <20180409002239.163177-1-alexander.levin@microsoft.com> In-Reply-To: <20180409002239.163177-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1; 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DIR:OUT; SFP:1102; SCL:1; SRVR:DM5PR2101MB0806; H:DM5PR2101MB1032.namprd21.prod.outlook.com; FPR:; SPF:None; LANG:en; PTR:InfoNoRecords; A:1; MX:1; received-spf: None (protection.outlook.com: microsoft.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: XxQAIEH+exP27PlsnBWaX1ypGExaaqEgVY0sT2yIKqpPiK5f2gHAHL921ak3XsJ+u9uEmPUsb3chzgM0K7O3YcNmkwSr07UiIEJ4Qt9mNw/kCASvb719FGfsaypzqtvDvgCVdRp6CXE2rk5ADp4uoOXWGqz0j+uDqnKPuUOy/5mak6oS+s+U+xmnMF1Afw1UXQc08JM67fdV4KrKexxyMSU2O2WA5VKK1VSUwrMYj3kBw85G6YWbJ6QrjZaf6pHzEaLJwFrTnPaYP5W+fU/yhJFN0+1Jm9j7X8FWBvah8gP5r48c+3RQaKXdXh5Lqe1rlsQu8AvqTJM+qv74fPFV+/XzZniWdG6kWv07xlQ8SzxcjMKCKzIN5TOgahGGlzsn0CJFgi0mI0NA9fTTUqyaFnqkkp13dAeOaFM7jhhML0Y= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9e1e4cc9-963b-4cea-aa9d-08d59db1b291 X-MS-Exchange-CrossTenant-originalarrivaltime: 09 Apr 2018 00:26:43.2384 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR2101MB0806 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Will Deacon [ Upstream commit 11dc13224c975efcec96647a4768a6f1bb7a19a8 ] When queuing on the qspinlock, the count field for the current CPU's head node is incremented. This needn't be atomic because locking in e.g. IRQ context is balanced and so an IRQ will return with node->count as it found it. However, the compiler could in theory reorder the initialisation of node[idx] before the increment of the head node->count, causing an IRQ to overwrite the initialised node and potentially corrupt the lock state. Avoid the potential for this harmful compiler reordering by placing a barrier() between the increment of the head node->count and the subsequent node initialisation. Signed-off-by: Will Deacon Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1518528177-19169-3-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- kernel/locking/qspinlock.c | 8 ++++++++ 1 file changed, 8 insertions(+) -- 2.15.1 diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c index b2caec7315af..a72f5df643f8 100644 --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -495,6 +495,14 @@ queue: tail = encode_tail(smp_processor_id(), idx); node += idx; + + /* + * Ensure that we increment the head node->count before initialising + * the actual node. If the compiler is kind enough to reorder these + * stores, then an IRQ could overwrite our assignments. + */ + barrier(); + node->locked = 0; node->next = NULL; pv_init_node(node);