From patchwork Thu Jan 26 03:33:55 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Demi Marie Obenour X-Patchwork-Id: 13116583 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 87B89C61DA0 for ; Thu, 26 Jan 2023 03:34:53 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.484688.751412 (Exim 4.92) (envelope-from ) id 1pKt1l-0008Ur-Qy; Thu, 26 Jan 2023 03:34:17 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 484688.751412; Thu, 26 Jan 2023 03:34:17 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1pKt1l-0008Uk-OM; 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bh=sHxeYo7zgfjFc cvxCuuph95svfpElxK2vn8+J41Up4A=; b=XIQCpZ3lX4/2fvGEl+smR04IQxUTp YuK64iAV32C+MVzzlelSu8NtBFy3/erKTDaWxxRgFI9OYqQVuQ/DJz9Tv+hoFKOm 4FxRc/bDupPlBYUU4UYdCHegdxMEunUBGzNtYiKm9AtHfexmQpZVGpBIxAahaA1T fvGb/rfnrO7ezrUMGViTPOF1DjPNXbqTAxFzq3hW9JBb0TLR8dNXWzO1JOmt26Eb tvOejPXmncG8791tijP4bM4Kd9ujFo1RIPbMn81uxM3JiB5xsMiPNiHHrpZi1QYx Yea9SHaJ1U7hOEBIAMxH2y4mx1MZa2AwwK0EUaeLP30w2vkPrVQp9AZWw== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvhedruddvfedgheelucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhephffvvefufffkofgjfhgggfestdekredtredttdenucfhrhhomhepffgvmhhi ucforghrihgvucfqsggvnhhouhhruceouggvmhhisehinhhvihhsihgslhgvthhhihhngh hslhgrsgdrtghomheqnecuggftrfgrthhtvghrnhepjeffjefggfeugeduvedvjeekgfeh gffhhfffjeetkeelueefffetfffhtdduheetnecuvehluhhsthgvrhfuihiivgeptdenuc frrghrrghmpehmrghilhhfrhhomhepuggvmhhisehinhhvihhsihgslhgvthhhihhnghhs lhgrsgdrtghomh X-ME-Proxy: Feedback-ID: iac594737:Fastmail From: Demi Marie Obenour To: =?utf-8?q?Roger_Pau_Monn=C3=A9?= , Juergen Gross , Jens Axboe Cc: Demi Marie Obenour , =?utf-8?q?Marek_Marczykowski?= =?utf-8?q?-G=C3=B3recki?= , xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Demi Marie Obenour Subject: [RFC PATCH 3/7] Implement diskseq checks in blkback Date: Wed, 25 Jan 2023 22:33:55 -0500 Message-Id: <20230126033358.1880-4-demi@invisiblethingslab.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230126033358.1880-1-demi@invisiblethingslab.com> References: <20230126033358.1880-1-demi@invisiblethingslab.com> MIME-Version: 1.0 From: Demi Marie Obenour 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. Older kernels will ignore this, so it is safe for userspace to set it unconditionally. This also makes physical-device parsing stricter. I do not believe this will break any extant userspace tools. Signed-off-by: Demi Marie Obenour --- drivers/block/xen-blkback/xenbus.c | 137 +++++++++++++++++++++-------- 1 file changed, 100 insertions(+), 37 deletions(-) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 4807af1d58059394d7a992335dabaf2bc3901721..2c43bfc7ab5ba6954f11d4b949a5668660dbd290 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 +508,25 @@ 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("xen_vbd_create: device %08x has no gendisk\n", + vbd->pdevice); + xen_vbd_free(vbd); + return -EFAULT; + } + + if (unlikely(disk->diskseq != diskseq)) { + pr_warn("xen_vbd_create: device %08x has incorrect sequence " + "number 0x%llx (expected 0x%llx)\n", + 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)) @@ -690,6 +710,55 @@ static int xen_blkbk_probe(struct xenbus_device *dev, return err; } +static bool read_physical_device(struct xenbus_device *dev, + unsigned long long *diskseq, + unsigned *major, unsigned *minor) +{ + char *physical_device, *problem; + int i, physical_device_length; + char junk; + + physical_device = xenbus_read(XBT_NIL, dev->nodename, "physical-device", + &physical_device_length); + + if (IS_ERR(physical_device)) { + int err = PTR_ERR(physical_device); + /* + * Since this watch will fire once immediately after it is + * registered, we expect "does not exist" errors. Ignore + * them and wait for the hotplug scripts. + */ + if (unlikely(!XENBUS_EXIST_ERR(err))) + xenbus_dev_fatal(dev, err, "reading physical-device"); + return false; + } + + for (i = 0; i < physical_device_length; ++i) + if (unlikely(physical_device[i] <= 0x20 || physical_device[i] >= 0x7F)) { + problem = "bad byte in physical-device"; + goto fail; + } + + if (sscanf(physical_device, "%16llx@%8x:%8x%c", + diskseq, major, minor, &junk) == 3) { + if (*diskseq == 0) { + problem = "diskseq 0 is invalid"; + goto fail; + } + } else if (sscanf(physical_device, "%8x:%8x%c", major, minor, &junk) == 2) { + *diskseq = 0; + } else { + problem = "invalid physical-device"; + goto fail; + } + kfree(physical_device); + return true; +fail: + kfree(physical_device); + xenbus_dev_fatal(dev, -EINVAL, problem); + return false; +} + /* * Callback received when the hotplug scripts have placed the physical-device * node. Read it and the mode node, and create a vbd. If the frontend is @@ -707,28 +776,17 @@ static void backend_changed(struct xenbus_watch *watch, int cdrom = 0; unsigned long handle; char *device_type; + unsigned long long diskseq; pr_debug("%s %p %d\n", __func__, dev, dev->otherend_id); - - err = xenbus_scanf(XBT_NIL, dev->nodename, "physical-device", "%x:%x", - &major, &minor); - if (XENBUS_EXIST_ERR(err)) { - /* - * Since this watch will fire once immediately after it is - * registered, we expect this. Ignore it, and wait for the - * hotplug scripts. - */ + if (!read_physical_device(dev, &diskseq, &major, &minor)) return; - } - if (err != 2) { - xenbus_dev_fatal(dev, err, "reading physical-device"); - 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); + 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 +814,34 @@ 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(be->mode); + be->mode = NULL; + be->major = 0; + be->minor = 0; + be->diskseq = 0; } /* From patchwork Thu Jan 26 03:33:57 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Demi Marie Obenour X-Patchwork-Id: 13116582 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id A2B66C54E94 for ; 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Signed-off-by: Demi Marie Obenour --- drivers/block/xen-blkback/blkback.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index a5cf7f1e871c7f9ff397ab8ff1d7b9e3db686659..8a49cbe81d8895f89371bdf50d1b445c088c9b6a 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -1238,6 +1238,8 @@ static int dispatch_rw_block_io(struct xen_blkif_ring *ring, nseg = req->operation == BLKIF_OP_INDIRECT ? req->u.indirect.nr_segments : req->u.rw.nr_segments; + BUILD_BUG_ON(offsetof(struct blkif_request, u.rw.id) != 8); + BUILD_BUG_ON(offsetof(struct blkif_request, u.indirect.id) != 8); if (unlikely(nseg == 0 && operation_flags != REQ_PREFLUSH) || unlikely((req->operation != BLKIF_OP_INDIRECT) && (nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) || @@ -1261,13 +1263,13 @@ static int dispatch_rw_block_io(struct xen_blkif_ring *ring, preq.sector_number = req->u.rw.sector_number; for (i = 0; i < nseg; i++) { pages[i]->gref = req->u.rw.seg[i].gref; - seg[i].nsec = req->u.rw.seg[i].last_sect - - req->u.rw.seg[i].first_sect + 1; - seg[i].offset = (req->u.rw.seg[i].first_sect << 9); if ((req->u.rw.seg[i].last_sect >= (XEN_PAGE_SIZE >> 9)) || (req->u.rw.seg[i].last_sect < req->u.rw.seg[i].first_sect)) goto fail_response; + seg[i].nsec = req->u.rw.seg[i].last_sect - + req->u.rw.seg[i].first_sect + 1; + seg[i].offset = (req->u.rw.seg[i].first_sect << 9); preq.nr_sects += seg[i].nsec; } } else { From patchwork Thu Jan 26 03:33:58 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Demi Marie Obenour X-Patchwork-Id: 13116584 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 7E557C61D97 for ; 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Protocol details are included in comments. Signed-off-by: Demi Marie Obenour --- drivers/block/xen-blkback/xenbus.c | 34 ++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c index 2c43bfc7ab5ba6954f11d4b949a5668660dbd290..ca8dae05985038da490c5ac93364509913f6b4c7 100644 --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -3,6 +3,19 @@ Copyright (C) 2005 Rusty Russell Copyright (C) 2005 XenSource Ltd +In addition to the XenStore nodes required by the Xen block device +specification, this implementation of blkback uses a new XenStore +node: "opened". blkback sets "opened" to "0" before the hotplug script +is called. Once the device node has been opened, blkback sets "opened" +to "1". + +"opened" is used exclusively by userspace. It serves two purposes: + +1. It tells userspace that diskseq@major:minor syntax for "physical-device" is + supported. +2. It tells userspace that it can wait for "opened" to be set to 1. Once + "opened" is 1, blkback has a reference to the device, so userspace doesn't + need to keep one. */ @@ -698,6 +711,14 @@ static int xen_blkbk_probe(struct xenbus_device *dev, if (err) pr_warn("%s write out 'max-ring-page-order' failed\n", __func__); + /* + * This informs userspace that the "opened" node will be set to "1" when + * the device has been opened successfully. + */ + err = xenbus_write(XBT_NIL, dev->nodename, "opened", "0"); + if (err) + goto fail; + err = xenbus_switch_state(dev, XenbusStateInitWait); if (err) goto fail; @@ -824,6 +845,19 @@ static void backend_changed(struct xenbus_watch *watch, goto fail; } + /* + * Tell userspace that the device has been opened and that blkback has a + * reference to it. Userspace can then close the device or mark it as + * delete-on-close, knowing that blkback will keep the device open as + * long as necessary. + */ + err = xenbus_write(XBT_NIL, dev->nodename, "opened", "1"); + if (err) { + xenbus_dev_fatal(dev, err, "%s: notifying userspace device has been opened", + dev->nodename); + goto free_vbd; + } + err = xenvbd_sysfs_addif(dev); if (err) { xenbus_dev_fatal(dev, err, "creating sysfs entries");