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[2620:137:e000::1:20]) by mx.google.com with ESMTP id v8-20020a170902b7c800b001b07c3c3206si293626plz.265.2023.06.01.15.19.32; Thu, 01 Jun 2023 15:19:46 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@invisiblethingslab.com header.s=fm1 header.b=PhGNaxRw; dkim=pass header.i=@messagingengine.com header.s=fm1 header.b=lpMBma0Y; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233197AbjFAVs5 (ORCPT + 99 others); Thu, 1 Jun 2023 17:48:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60692 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232959AbjFAVsf (ORCPT ); Thu, 1 Jun 2023 17:48:35 -0400 Received: from out3-smtp.messagingengine.com (out3-smtp.messagingengine.com [66.111.4.27]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCE0319D; Thu, 1 Jun 2023 14:48:33 -0700 (PDT) Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.nyi.internal (Postfix) with ESMTP id 101F55C0196; Thu, 1 Jun 2023 17:48:33 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute3.internal (MEProxy); Thu, 01 Jun 2023 17:48:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= invisiblethingslab.com; h=cc:cc:content-transfer-encoding :content-type:date:date:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:sender:subject :subject:to:to; s=fm1; t=1685656113; x=1685742513; bh=KqvPH9pDDf rZerL/j1Q0a8RK2jTSm93zECezjcEfZ7Y=; b=PhGNaxRwheqgbYSVaXU75pFKw2 6MGTNaRUtrwir0W9wwvwQ0fEbeDSYwccxCit81zpBGFIz1J2MyvsJphlcw3O6cjl ETmq9Spmk/VIkE5vAet7+10uyDswVQjcvD0oO1/f/MrvWLljpd1MmKfV0R0N3jQ+ qEroWWUgVcB09PTiNaFQLnLqqThnpQ7WX9P5KRA/Q6Ki/3IAoP6ROhP0v0vzuebl jW+AnQMCg64nuru4QVSBS76ola9YvwzJjpy6TsRgBbg9/qW9f54zasEyDyR8X+gE teYfc8Ead4FtC9G/mqPk3RqICvy5hHM0jYnnoNO9KC1u2ohApIASi1XuY5lw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:date:date:feedback-id:feedback-id:from:from :in-reply-to:in-reply-to:message-id:mime-version:references :reply-to:sender:subject:subject:to:to:x-me-proxy:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm1; t=1685656113; x= 1685742513; bh=KqvPH9pDDfrZerL/j1Q0a8RK2jTSm93zECezjcEfZ7Y=; b=l pMBma0YclrB4aMeW+ve6wNTxXVlURGumwBt/LHcnMqY+i50kjHcj5COrD2FOIfh8 GH25Wnh/bo/6dbhVlZeiU9XdQH0Q/D2u7WkvqUfiEWcVX2uQhKIM/Gtqb6lsi9+n H5eUBRs8lyi+EIUOpG8YiFrRERtDsYMZZtyhRfD7HZaEMZQh5Ivbd4pFC4Dc9r91 HjwdPF26FcVuja/OVmDzO1XLCD0CswZGLmaJY3t0NRLjJDFfKCmLJrqRG7AdlkoJ FT3HA0ssnXWLr97XazuqMgkWVLGX1nKJnDDL+cFSEp8P+a6Bd9USjnZCySzhR3pU c8nC+NiWw8GH8KlQyjIzg== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvhedrfeelvddgtddvucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhephffvvefufffkofgjfhgggfestdekredtredttdenucfhrhhomhepffgvmhhi ucforghrihgvucfqsggvnhhouhhruceouggvmhhisehinhhvihhsihgslhgvthhhihhngh hslhgrsgdrtghomheqnecuggftrfgrthhtvghrnhepjeffjefggfeugeduvedvjeekgfeh gffhhfffjeetkeelueefffetfffhtdduheetnecuvehluhhsthgvrhfuihiivgeptdenuc frrghrrghmpehmrghilhhfrhhomhepuggvmhhisehinhhvihhsihgslhgvthhhihhnghhs lhgrsgdrtghomh X-ME-Proxy: Feedback-ID: iac594737:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Thu, 1 Jun 2023 17:48:32 -0400 (EDT) From: Demi Marie Obenour To: =?utf-8?q?Roger_Pau_Monn=C3=A9?= , Jens Axboe Cc: Demi Marie Obenour , =?utf-8?q?Marek_Marczy?= =?utf-8?q?kowski-G=C3=B3recki?= , xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/2] xen-blkback: Implement diskseq checks Date: Thu, 1 Jun 2023 17:48:22 -0400 Message-Id: <20230601214823.1701-2-demi@invisiblethingslab.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230601214823.1701-1-demi@invisiblethingslab.com> References: <20230601214823.1701-1-demi@invisiblethingslab.com> MIME-Version: 1.0 X-Spam-Status: No, score=-2.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS, SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1767540508691767718?= X-GMAIL-MSGID: =?utf-8?q?1767540508691767718?= This allows specifying a disk sequence number in XenStore. If it does not match the disk sequence number of the underlying device, the device will not be exported and a warning will be logged. Userspace can use this to eliminate race conditions due to major/minor number reuse. Old kernels do not support the new syntax, but a later patch will allow userspace to discover that the new syntax is supported. Signed-off-by: Demi Marie Obenour --- drivers/block/xen-blkback/xenbus.c | 112 +++++++++++++++++++++++------ 1 file changed, 89 insertions(+), 23 deletions(-) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 4807af1d58059394d7a992335dabaf2bc3901721..9c3eb148fbd802c74e626c3d7bcd69dcb09bd921 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -24,6 +24,7 @@ struct backend_info { struct xenbus_watch backend_watch; unsigned major; unsigned minor; + unsigned long long diskseq; char *mode; }; @@ -479,7 +480,7 @@ static void xen_vbd_free(struct xen_vbd *vbd) static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, unsigned major, unsigned minor, int readonly, - int cdrom) + bool cdrom, u64 diskseq) { struct xen_vbd *vbd; struct block_device *bdev; @@ -507,6 +508,26 @@ static int xen_vbd_create(struct xen_blkif *blkif, blkif_vdev_t handle, xen_vbd_free(vbd); return -ENOENT; } + + if (diskseq) { + struct gendisk *disk = bdev->bd_disk; + + if (unlikely(disk == NULL)) { + pr_err("%s: device %08x has no gendisk\n", + __func__, vbd->pdevice); + xen_vbd_free(vbd); + return -EFAULT; + } + + if (unlikely(disk->diskseq != diskseq)) { + pr_warn("%s: device %08x has incorrect sequence " + "number 0x%llx (expected 0x%llx)\n", + __func__, vbd->pdevice, disk->diskseq, diskseq); + xen_vbd_free(vbd); + return -ENODEV; + } + } + vbd->size = vbd_sz(vbd); if (cdrom || disk_to_cdi(vbd->bdev->bd_disk)) @@ -707,6 +728,9 @@ static void backend_changed(struct xenbus_watch *watch, int cdrom = 0; unsigned long handle; char *device_type; + char *diskseq_str = NULL; + int diskseq_len; + unsigned long long diskseq; pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id); @@ -725,10 +749,46 @@ static void backend_changed(struct xenbus_watch *watch, return; } - if (be->major | be->minor) { - if (be->major != major || be->minor != minor) - pr_warn("changing physical device (from %x:%x to %x:%x) not supported.\n", - be->major, be->minor, major, minor); + diskseq_str = xenbus_read(XBT_NIL, dev->nodename, "diskseq", &diskseq_len); + if (IS_ERR(diskseq_str)) { + int err = PTR_ERR(diskseq_str); + diskseq_str = NULL; + + /* + * If this does not exist, it means legacy userspace that does not + * support diskseq. + */ + if (unlikely(!XENBUS_EXIST_ERR(err))) { + xenbus_dev_fatal(dev, err, "reading diskseq"); + return; + } + diskseq = 0; + } else if (diskseq_len <= 0) { + xenbus_dev_fatal(dev, -EFAULT, "diskseq must not be empty"); + goto fail; + } else if (diskseq_len > 16) { + xenbus_dev_fatal(dev, -ERANGE, "diskseq too long: got %d but limit is 16", + diskseq_len); + goto fail; + } else if (diskseq_str[0] == '0') { + xenbus_dev_fatal(dev, -ERANGE, "diskseq must not start with '0'"); + goto fail; + } else { + char *diskseq_end; + diskseq = simple_strtoull(diskseq_str, &diskseq_end, 16); + if (diskseq_end != diskseq_str + diskseq_len) { + xenbus_dev_fatal(dev, -EINVAL, "invalid diskseq"); + goto fail; + } + kfree(diskseq_str); + diskseq_str = NULL; + } + + if (be->major | be->minor | be->diskseq) { + if (be->major != major || be->minor != minor || be->diskseq != diskseq) + pr_warn("changing physical device (from %x:%x:%llx to %x:%x:%llx)" + " not supported.\n", + be->major, be->minor, be->diskseq, major, minor, diskseq); return; } @@ -756,29 +816,35 @@ static void backend_changed(struct xenbus_watch *watch, be->major = major; be->minor = minor; + be->diskseq = diskseq; err = xen_vbd_create(be->blkif, handle, major, minor, - !strchr(be->mode, 'w'), cdrom); - - if (err) - xenbus_dev_fatal(dev, err, "creating vbd structure"); - else { - err = xenvbd_sysfs_addif(dev); - if (err) { - xen_vbd_free(&be->blkif->vbd); - xenbus_dev_fatal(dev, err, "creating sysfs entries"); - } - } + !strchr(be->mode, 'w'), cdrom, diskseq); if (err) { - kfree(be->mode); - be->mode = NULL; - be->major = 0; - be->minor = 0; - } else { - /* We're potentially connected now */ - xen_update_blkif_status(be->blkif); + xenbus_dev_fatal(dev, err, "creating vbd structure"); + goto fail; } + + err = xenvbd_sysfs_addif(dev); + if (err) { + xenbus_dev_fatal(dev, err, "creating sysfs entries"); + goto free_vbd; + } + + /* We're potentially connected now */ + xen_update_blkif_status(be->blkif); + return; + +free_vbd: + xen_vbd_free(&be->blkif->vbd); +fail: + kfree(diskseq_str); + kfree(be->mode); + be->mode = NULL; + be->major = 0; + be->minor = 0; + be->diskseq = 0; } /*