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=-9.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 AC44AC5ACC0 for ; Mon, 16 Mar 2020 02:34:46 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7DFA120726 for ; Mon, 16 Mar 2020 02:34:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Kf33GIac" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7DFA120726 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jDfZt-0004sP-0A; Mon, 16 Mar 2020 02:34:05 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jDfZs-0004sK-B3 for xen-devel@lists.xenproject.org; Mon, 16 Mar 2020 02:34:04 +0000 X-Inumbo-ID: 99ce3de2-672e-11ea-b769-12813bfff9fa Received: from mail.kernel.org (unknown [198.145.29.99]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 99ce3de2-672e-11ea-b769-12813bfff9fa; Mon, 16 Mar 2020 02:34:03 +0000 (UTC) Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 66FF0206EB; Mon, 16 Mar 2020 02:34:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584326043; bh=8utJ4PbiBkJFqLWavO/QYmjVPSaB2McN1fDCS3CNWwg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Kf33GIacZxdQb+WRd5kZqTQXVmg0KYqxjAr8GHdw2qvVCQQjE1ZzSbKDXRhbbJBbG nXZfQkdafcqQBZrJvUc3TUEXNS7pn2vOWvpWG5d2Mtg9ezUhSUtMSI9qPl5faepKmn KaUY+w3JJ4CQSGu/8Pblu79JkiI4jYSnO08RHnfc= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Date: Sun, 15 Mar 2020 22:33:14 -0400 Message-Id: <20200316023319.749-36-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200316023319.749-1-sashal@kernel.org> References: <20200316023319.749-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Subject: [Xen-devel] [PATCH AUTOSEL 5.5 36/41] xenbus: req->body should be updated before req->state X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Sasha Levin , Dongli Zhang , Julien Grall , Boris Ostrovsky , xen-devel@lists.xenproject.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" RnJvbTogRG9uZ2xpIFpoYW5nIDxkb25nbGkuemhhbmdAb3JhY2xlLmNvbT4KClsgVXBzdHJlYW0g Y29tbWl0IDFiNmE1MWU4NmNjZTM4Y2Y0ZDQ4Y2U5YzI0MjEyMDI4M2FlMmY2MDMgXQoKVGhlIHJl cS0+Ym9keSBzaG91bGQgYmUgdXBkYXRlZCBiZWZvcmUgcmVxLT5zdGF0ZSBpcyB1cGRhdGVkIGFu ZCB0aGUKb3JkZXIgc2hvdWxkIGJlIGd1YXJhbnRlZWQgYnkgYSBiYXJyaWVyLgoKT3RoZXJ3aXNl LCByZWFkX3JlcGx5KCkgbWlnaHQgcmV0dXJuIHJlcS0+Ym9keSA9IE5VTEwuCgpCZWxvdyBpcyBz YW1wbGUgY2FsbHN0YWNrIHdoZW4gdGhlIGlzc3VlIGlzIHJlcHJvZHVjZWQgb24gcHVycG9zZSBi eQpyZW9yZGVyaW5nIHRoZSB1cGRhdGVzIG9mIHJlcS0+Ym9keSBhbmQgcmVxLT5zdGF0ZSBhbmQg YWRkaW5nIGRlbGF5IGluCmNvZGUgYmV0d2VlbiB1cGRhdGVzIG9mIHJlcS0+c3RhdGUgYW5kIHJl cS0+Ym9keS4KClsgICAyMi4zNTYxMDVdIGdlbmVyYWwgcHJvdGVjdGlvbiBmYXVsdDogMDAwMCBb IzFdIFNNUCBQVEkKWyAgIDIyLjM2MTE4NV0gQ1BVOiAyIFBJRDogNTIgQ29tbTogeGVud2F0Y2gg Tm90IHRhaW50ZWQgNS41LjB4ZW4rICM2ClsgICAyMi4zNjY3MjddIEhhcmR3YXJlIG5hbWU6IFhl biBIVk0gZG9tVSwgQklPUyAuLi4KWyAgIDIyLjM3MjI0NV0gUklQOiAwMDEwOl9wYXJzZV9pbnRl Z2VyX2ZpeHVwX3JhZGl4KzB4Ni8weDYwCi4uLiAuLi4KWyAgIDIyLjM5MjE2M10gUlNQOiAwMDE4 OmZmZmZiMmQ2NDAyM2ZkZjAgRUZMQUdTOiAwMDAxMDI0NgpbICAgMjIuMzk1OTMzXSBSQVg6IDAw MDAwMDAwMDAwMDAwMDAgUkJYOiA3NTc0NmU3NTYyNzU1ZjZkIFJDWDogMDAwMDAwMDAwMDAwMDAw MApbICAgMjIuNDAwODcxXSBSRFg6IDAwMDAwMDAwMDAwMDAwMDAgUlNJOiBmZmZmYjJkNjQwMjNm ZGZjIFJESTogNzU3NDZlNzU2Mjc1NWY2ZApbICAgMjIuNDA1ODc0XSBSQlA6IDAwMDAwMDAwMDAw MDAwMDAgUjA4OiAwMDAwMDAwMDAwMDAwMWU4IFIwOTogMDAwMDAwMDAwMGNkY2RjZApbICAgMjIu NDEwOTQ1XSBSMTA6IGZmZmZiMmQ2NDAyZmZlMDAgUjExOiBmZmZmOWQ5NTM5NWVhZWIwIFIxMjog ZmZmZjlkOTUzNTkzNTAwMApbICAgMjIuNDE3NjEzXSBSMTM6IGZmZmY5ZDk1MjZkNGEwMDAgUjE0 OiBmZmZmOWQ5NTI2ZjRmMzQwIFIxNTogZmZmZjlkOTUzNzY1NDAwMApbICAgMjIuNDIzNzI2XSBG UzogIDAwMDAwMDAwMDAwMDAwMDAoMDAwMCkgR1M6ZmZmZjlkOTUzYmM4MDAwMCgwMDAwKSBrbmxH UzowMDAwMDAwMDAwMDAwMDAwClsgICAyMi40Mjk4OThdIENTOiAgMDAxMCBEUzogMDAwMCBFUzog MDAwMCBDUjA6IDAwMDAwMDAwODAwNTAwMzMKWyAgIDIyLjQzNDM0Ml0gQ1IyOiAwMDAwMDBjNDIw NmE5MDAwIENSMzogMDAwMDAwMDFlYTNmYzAwMiBDUjQ6IDAwMDAwMDAwMDAxNjA2ZTAKWyAgIDIy LjQzOTY0NV0gRFIwOiAwMDAwMDAwMDAwMDAwMDAwIERSMTogMDAwMDAwMDAwMDAwMDAwMCBEUjI6 IDAwMDAwMDAwMDAwMDAwMDAKWyAgIDIyLjQ0NDk0MV0gRFIzOiAwMDAwMDAwMDAwMDAwMDAwIERS NjogMDAwMDAwMDBmZmZlMGZmMCBEUjc6IDAwMDAwMDAwMDAwMDA0MDAKWyAgIDIyLjQ1MDM0Ml0g Q2FsbCBUcmFjZToKWyAgIDIyLjQ1MjUwOV0gIHNpbXBsZV9zdHJ0b3VsbCsweDI3LzB4NzAKWyAg IDIyLjQ1NTU3Ml0gIHhlbmJ1c190cmFuc2FjdGlvbl9zdGFydCsweDMxLzB4NTAKWyAgIDIyLjQ1 OTEwNF0gIG5ldGJhY2tfY2hhbmdlZCsweDc2Yy8weGNjMSBbeGVuX25ldGZyb250XQpbICAgMjIu NDYzMjc5XSAgPyBmaW5kX3dhdGNoKzB4NDAvMHg0MApbICAgMjIuNDY2MTU2XSAgeGVud2F0Y2hf dGhyZWFkKzB4YjQvMHgxNTAKWyAgIDIyLjQ2OTMwOV0gID8gd2FpdF93b2tlbisweDgwLzB4ODAK WyAgIDIyLjQ3MjE5OF0gIGt0aHJlYWQrMHgxMGUvMHgxMzAKWyAgIDIyLjQ3NDkyNV0gID8ga3Ro cmVhZF9wYXJrKzB4ODAvMHg4MApbICAgMjIuNDc3OTQ2XSAgcmV0X2Zyb21fZm9yaysweDM1LzB4 NDAKWyAgIDIyLjQ4MDk2OF0gTW9kdWxlcyBsaW5rZWQgaW46IHhlbl9rYmRmcm9udCB4ZW5fZmJm cm9udCgrKSB4ZW5fbmV0ZnJvbnQgeGVuX2Jsa2Zyb250ClsgICAyMi40ODY3ODNdIC0tLVsgZW5k IHRyYWNlIGE5MjIyMDMwYTc0N2MzZjcgXS0tLQpbICAgMjIuNDkwNDI0XSBSSVA6IDAwMTA6X3Bh cnNlX2ludGVnZXJfZml4dXBfcmFkaXgrMHg2LzB4NjAKClRoZSB2aXJ0X3JtYigpIGlzIGFkZGVk IGluIHRoZSAndHJ1ZScgcGF0aCBvZiB0ZXN0X3JlcGx5KCkuIFRoZSAid2hpbGUiCmlzIGNoYW5n ZWQgdG8gImRvIHdoaWxlIiBzbyB0aGF0IHRlc3RfcmVwbHkoKSBpcyB1c2VkIGFzIGEgcmVhZCBt ZW1vcnkKYmFycmllci4KClNpZ25lZC1vZmYtYnk6IERvbmdsaSBaaGFuZyA8ZG9uZ2xpLnpoYW5n QG9yYWNsZS5jb20+Ckxpbms6IGh0dHBzOi8vbG9yZS5rZXJuZWwub3JnL3IvMjAyMDAzMDMyMjE0 MjMuMjE5NjItMS1kb25nbGkuemhhbmdAb3JhY2xlLmNvbQpSZXZpZXdlZC1ieTogSnVsaWVuIEdy YWxsIDxqZ3JhbGxAYW1hem9uLmNvbT4KU2lnbmVkLW9mZi1ieTogQm9yaXMgT3N0cm92c2t5IDxi b3Jpcy5vc3Ryb3Zza3lAb3JhY2xlLmNvbT4KU2lnbmVkLW9mZi1ieTogU2FzaGEgTGV2aW4gPHNh c2hhbEBrZXJuZWwub3JnPgotLS0KIGRyaXZlcnMveGVuL3hlbmJ1cy94ZW5idXNfY29tbXMuYyB8 IDIgKysKIGRyaXZlcnMveGVuL3hlbmJ1cy94ZW5idXNfeHMuYyAgICB8IDkgKysrKysrLS0tCiAy IGZpbGVzIGNoYW5nZWQsIDggaW5zZXJ0aW9ucygrKSwgMyBkZWxldGlvbnMoLSkKCmRpZmYgLS1n aXQgYS9kcml2ZXJzL3hlbi94ZW5idXMveGVuYnVzX2NvbW1zLmMgYi9kcml2ZXJzL3hlbi94ZW5i dXMveGVuYnVzX2NvbW1zLmMKaW5kZXggZDIzOWZjM2M1ZTNkZS4uODUyZWQxNjFmYzJhNyAxMDA2 NDQKLS0tIGEvZHJpdmVycy94ZW4veGVuYnVzL3hlbmJ1c19jb21tcy5jCisrKyBiL2RyaXZlcnMv eGVuL3hlbmJ1cy94ZW5idXNfY29tbXMuYwpAQCAtMzEzLDYgKzMxMyw4IEBAIHN0YXRpYyBpbnQg cHJvY2Vzc19tc2codm9pZCkKIAkJCXJlcS0+bXNnLnR5cGUgPSBzdGF0ZS5tc2cudHlwZTsKIAkJ CXJlcS0+bXNnLmxlbiA9IHN0YXRlLm1zZy5sZW47CiAJCQlyZXEtPmJvZHkgPSBzdGF0ZS5ib2R5 OworCQkJLyogd3JpdGUgYm9keSwgdGhlbiB1cGRhdGUgc3RhdGUgKi8KKwkJCXZpcnRfd21iKCk7 CiAJCQlyZXEtPnN0YXRlID0geGJfcmVxX3N0YXRlX2dvdF9yZXBseTsKIAkJCXJlcS0+Y2IocmVx KTsKIAkJfSBlbHNlCmRpZmYgLS1naXQgYS9kcml2ZXJzL3hlbi94ZW5idXMveGVuYnVzX3hzLmMg Yi9kcml2ZXJzL3hlbi94ZW5idXMveGVuYnVzX3hzLmMKaW5kZXggZGRjMThkYTYxODM0ZS4uM2Ew NmViNjk5ZjMzMyAxMDA2NDQKLS0tIGEvZHJpdmVycy94ZW4veGVuYnVzL3hlbmJ1c194cy5jCisr KyBiL2RyaXZlcnMveGVuL3hlbmJ1cy94ZW5idXNfeHMuYwpAQCAtMTkxLDggKzE5MSwxMSBAQCBz dGF0aWMgYm9vbCB4ZW5idXNfb2sodm9pZCkKIAogc3RhdGljIGJvb2wgdGVzdF9yZXBseShzdHJ1 Y3QgeGJfcmVxX2RhdGEgKnJlcSkKIHsKLQlpZiAocmVxLT5zdGF0ZSA9PSB4Yl9yZXFfc3RhdGVf Z290X3JlcGx5IHx8ICF4ZW5idXNfb2soKSkKKwlpZiAocmVxLT5zdGF0ZSA9PSB4Yl9yZXFfc3Rh dGVfZ290X3JlcGx5IHx8ICF4ZW5idXNfb2soKSkgeworCQkvKiByZWFkIHJlcS0+c3RhdGUgYmVm b3JlIGFsbCBvdGhlciBmaWVsZHMgKi8KKwkJdmlydF9ybWIoKTsKIAkJcmV0dXJuIHRydWU7CisJ fQogCiAJLyogTWFrZSBzdXJlIHRvIHJlcmVhZCByZXEtPnN0YXRlIGVhY2ggdGltZS4gKi8KIAli YXJyaWVyKCk7CkBAIC0yMDIsNyArMjA1LDcgQEAgc3RhdGljIGJvb2wgdGVzdF9yZXBseShzdHJ1 Y3QgeGJfcmVxX2RhdGEgKnJlcSkKIAogc3RhdGljIHZvaWQgKnJlYWRfcmVwbHkoc3RydWN0IHhi X3JlcV9kYXRhICpyZXEpCiB7Ci0Jd2hpbGUgKHJlcS0+c3RhdGUgIT0geGJfcmVxX3N0YXRlX2dv dF9yZXBseSkgeworCWRvIHsKIAkJd2FpdF9ldmVudChyZXEtPndxLCB0ZXN0X3JlcGx5KHJlcSkp OwogCiAJCWlmICgheGVuYnVzX29rKCkpCkBAIC0yMTYsNyArMjE5LDcgQEAgc3RhdGljIHZvaWQg KnJlYWRfcmVwbHkoc3RydWN0IHhiX3JlcV9kYXRhICpyZXEpCiAJCWlmIChyZXEtPmVycikKIAkJ CXJldHVybiBFUlJfUFRSKHJlcS0+ZXJyKTsKIAotCX0KKwl9IHdoaWxlIChyZXEtPnN0YXRlICE9 IHhiX3JlcV9zdGF0ZV9nb3RfcmVwbHkpOwogCiAJcmV0dXJuIHJlcS0+Ym9keTsKIH0KLS0gCjIu MjAuMQoKCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fClhl bi1kZXZlbCBtYWlsaW5nIGxpc3QKWGVuLWRldmVsQGxpc3RzLnhlbnByb2plY3Qub3JnCmh0dHBz Oi8vbGlzdHMueGVucHJvamVjdC5vcmcvbWFpbG1hbi9saXN0aW5mby94ZW4tZGV2ZWw= 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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 73784C10F29 for ; Mon, 16 Mar 2020 02:34:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A2B120737 for ; Mon, 16 Mar 2020 02:34:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584326048; bh=8utJ4PbiBkJFqLWavO/QYmjVPSaB2McN1fDCS3CNWwg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Ju8LJRSn3rMOSQ8SzRPwX+KRgJO4lePuDyyFlLGr4sulmHRpDAUXq5hoj/oGUsmg0 LQp3zX+Sv11fhXKse/Ffltg4a+dHCVgoWZEpflJ5ufAFNaJqNoPNXew02B0ZnntFvo 0U8BFTbtOdMknWbP6TkiTAW0+mHlswDPJT9/rtbc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729752AbgCPCeH (ORCPT ); Sun, 15 Mar 2020 22:34:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:37158 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729730AbgCPCeE (ORCPT ); Sun, 15 Mar 2020 22:34:04 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 66FF0206EB; Mon, 16 Mar 2020 02:34:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584326043; bh=8utJ4PbiBkJFqLWavO/QYmjVPSaB2McN1fDCS3CNWwg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Kf33GIacZxdQb+WRd5kZqTQXVmg0KYqxjAr8GHdw2qvVCQQjE1ZzSbKDXRhbbJBbG nXZfQkdafcqQBZrJvUc3TUEXNS7pn2vOWvpWG5d2Mtg9ezUhSUtMSI9qPl5faepKmn KaUY+w3JJ4CQSGu/8Pblu79JkiI4jYSnO08RHnfc= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Dongli Zhang , Julien Grall , Boris Ostrovsky , Sasha Levin , xen-devel@lists.xenproject.org Subject: [PATCH AUTOSEL 5.5 36/41] xenbus: req->body should be updated before req->state Date: Sun, 15 Mar 2020 22:33:14 -0400 Message-Id: <20200316023319.749-36-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200316023319.749-1-sashal@kernel.org> References: <20200316023319.749-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dongli Zhang [ Upstream commit 1b6a51e86cce38cf4d48ce9c242120283ae2f603 ] The req->body should be updated before req->state is updated and the order should be guaranteed by a barrier. Otherwise, read_reply() might return req->body = NULL. Below is sample callstack when the issue is reproduced on purpose by reordering the updates of req->body and req->state and adding delay in code between updates of req->state and req->body. [ 22.356105] general protection fault: 0000 [#1] SMP PTI [ 22.361185] CPU: 2 PID: 52 Comm: xenwatch Not tainted 5.5.0xen+ #6 [ 22.366727] Hardware name: Xen HVM domU, BIOS ... [ 22.372245] RIP: 0010:_parse_integer_fixup_radix+0x6/0x60 ... ... [ 22.392163] RSP: 0018:ffffb2d64023fdf0 EFLAGS: 00010246 [ 22.395933] RAX: 0000000000000000 RBX: 75746e7562755f6d RCX: 0000000000000000 [ 22.400871] RDX: 0000000000000000 RSI: ffffb2d64023fdfc RDI: 75746e7562755f6d [ 22.405874] RBP: 0000000000000000 R08: 00000000000001e8 R09: 0000000000cdcdcd [ 22.410945] R10: ffffb2d6402ffe00 R11: ffff9d95395eaeb0 R12: ffff9d9535935000 [ 22.417613] R13: ffff9d9526d4a000 R14: ffff9d9526f4f340 R15: ffff9d9537654000 [ 22.423726] FS: 0000000000000000(0000) GS:ffff9d953bc80000(0000) knlGS:0000000000000000 [ 22.429898] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 22.434342] CR2: 000000c4206a9000 CR3: 00000001ea3fc002 CR4: 00000000001606e0 [ 22.439645] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 22.444941] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 22.450342] Call Trace: [ 22.452509] simple_strtoull+0x27/0x70 [ 22.455572] xenbus_transaction_start+0x31/0x50 [ 22.459104] netback_changed+0x76c/0xcc1 [xen_netfront] [ 22.463279] ? find_watch+0x40/0x40 [ 22.466156] xenwatch_thread+0xb4/0x150 [ 22.469309] ? wait_woken+0x80/0x80 [ 22.472198] kthread+0x10e/0x130 [ 22.474925] ? kthread_park+0x80/0x80 [ 22.477946] ret_from_fork+0x35/0x40 [ 22.480968] Modules linked in: xen_kbdfront xen_fbfront(+) xen_netfront xen_blkfront [ 22.486783] ---[ end trace a9222030a747c3f7 ]--- [ 22.490424] RIP: 0010:_parse_integer_fixup_radix+0x6/0x60 The virt_rmb() is added in the 'true' path of test_reply(). The "while" is changed to "do while" so that test_reply() is used as a read memory barrier. Signed-off-by: Dongli Zhang Link: https://lore.kernel.org/r/20200303221423.21962-1-dongli.zhang@oracle.com Reviewed-by: Julien Grall Signed-off-by: Boris Ostrovsky Signed-off-by: Sasha Levin --- drivers/xen/xenbus/xenbus_comms.c | 2 ++ drivers/xen/xenbus/xenbus_xs.c | 9 ++++++--- 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/xen/xenbus/xenbus_comms.c b/drivers/xen/xenbus/xenbus_comms.c index d239fc3c5e3de..852ed161fc2a7 100644 --- a/drivers/xen/xenbus/xenbus_comms.c +++ b/drivers/xen/xenbus/xenbus_comms.c @@ -313,6 +313,8 @@ static int process_msg(void) req->msg.type = state.msg.type; req->msg.len = state.msg.len; req->body = state.body; + /* write body, then update state */ + virt_wmb(); req->state = xb_req_state_got_reply; req->cb(req); } else diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c index ddc18da61834e..3a06eb699f333 100644 --- a/drivers/xen/xenbus/xenbus_xs.c +++ b/drivers/xen/xenbus/xenbus_xs.c @@ -191,8 +191,11 @@ static bool xenbus_ok(void) static bool test_reply(struct xb_req_data *req) { - if (req->state == xb_req_state_got_reply || !xenbus_ok()) + if (req->state == xb_req_state_got_reply || !xenbus_ok()) { + /* read req->state before all other fields */ + virt_rmb(); return true; + } /* Make sure to reread req->state each time. */ barrier(); @@ -202,7 +205,7 @@ static bool test_reply(struct xb_req_data *req) static void *read_reply(struct xb_req_data *req) { - while (req->state != xb_req_state_got_reply) { + do { wait_event(req->wq, test_reply(req)); if (!xenbus_ok()) @@ -216,7 +219,7 @@ static void *read_reply(struct xb_req_data *req) if (req->err) return ERR_PTR(req->err); - } + } while (req->state != xb_req_state_got_reply); return req->body; } -- 2.20.1