From patchwork Mon May 18 17:35:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 225769 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=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, 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 4E727C433E0 for ; Mon, 18 May 2020 18:00:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 26945207F5 for ; Mon, 18 May 2020 18:00:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589824837; bh=ZeaT1UWrh+ajkitvCxbSYqAIcX3Pf1/t8+3JjVNaooo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=z+JItJl8k51cgU9RF9d/lI2aBpE4Hd/Z04yRVSm8ijWkq7IrLtGHiCAeSCuv121zK LLc4omT7X0D2Z4E0FacS1H4i1sx0bffGb7Qb97lxKWBZ/R/9yTJHhdtksi9eWCEA9H +SIkR1CqULAaMjdVLMMZEx8Cg3Pf3VArH5AKQyHE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732237AbgERSAd (ORCPT ); Mon, 18 May 2020 14:00:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:42092 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732235AbgERSAc (ORCPT ); Mon, 18 May 2020 14:00:32 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5DCB420715; Mon, 18 May 2020 18:00:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589824831; bh=ZeaT1UWrh+ajkitvCxbSYqAIcX3Pf1/t8+3JjVNaooo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ko0eQiWJD3Q4c6esq/SiA6Xy6hV9DYxQIZfg/bvFN39cpN3tSrGhjJVhbWMgKPX5q bG+fIDvZEHoz6dKWcutonhAtFO3xPB6JXcKSJ9gHce/UoOPDTuFmK6uMNE4KkTidpR upDnKJdlBUl6f2/NCamorSYKuivRkq5Gpyw9zDOE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Lance Digby , Stefan Hajnoczi , "Michael S. Tsirkin" , Stefano Garzarella , Sasha Levin Subject: [PATCH 5.6 021/194] virtio-blk: handle block_device_operations callbacks after hot unplug Date: Mon, 18 May 2020 19:35:11 +0200 Message-Id: <20200518173533.299435351@linuxfoundation.org> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200518173531.455604187@linuxfoundation.org> References: <20200518173531.455604187@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Stefan Hajnoczi [ Upstream commit 90b5feb8c4bebc76c27fcaf3e1a0e5ca2d319e9e ] A userspace process holding a file descriptor to a virtio_blk device can still invoke block_device_operations after hot unplug. This leads to a use-after-free accessing vblk->vdev in virtblk_getgeo() when ioctl(HDIO_GETGEO) is invoked: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [] virtio_check_driver_offered_feature+0x10/0x90 [virtio] PGD 800000003a92f067 PUD 3a930067 PMD 0 Oops: 0000 [#1] SMP CPU: 0 PID: 1310 Comm: hdio-getgeo Tainted: G OE ------------ 3.10.0-1062.el7.x86_64 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 task: ffff9be5fbfb8000 ti: ffff9be5fa890000 task.ti: ffff9be5fa890000 RIP: 0010:[] [] virtio_check_driver_offered_feature+0x10/0x90 [virtio] RSP: 0018:ffff9be5fa893dc8 EFLAGS: 00010246 RAX: ffff9be5fc3f3400 RBX: ffff9be5fa893e30 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff9be5fbc10b40 RBP: ffff9be5fa893dc8 R08: 0000000000000301 R09: 0000000000000301 R10: 0000000000000000 R11: 0000000000000000 R12: ffff9be5fdc24680 R13: ffff9be5fbc10b40 R14: ffff9be5fbc10480 R15: 0000000000000000 FS: 00007f1bfb968740(0000) GS:ffff9be5ffc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000090 CR3: 000000003a894000 CR4: 0000000000360ff0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: [] virtblk_getgeo+0x47/0x110 [virtio_blk] [] ? handle_mm_fault+0x39d/0x9b0 [] blkdev_ioctl+0x1f5/0xa20 [] block_ioctl+0x41/0x50 [] do_vfs_ioctl+0x3a0/0x5a0 [] SyS_ioctl+0xa1/0xc0 A related problem is that virtblk_remove() leaks the vd_index_ida index when something still holds a reference to vblk->disk during hot unplug. This causes virtio-blk device names to be lost (vda, vdb, etc). Fix these issues by protecting vblk->vdev with a mutex and reference counting vblk so the vd_index_ida index can be removed in all cases. Fixes: 48e4043d4529 ("virtio: add virtio disk geometry feature") Reported-by: Lance Digby Signed-off-by: Stefan Hajnoczi Link: https://lore.kernel.org/r/20200430140442.171016-1-stefanha@redhat.com Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefano Garzarella Signed-off-by: Sasha Levin --- drivers/block/virtio_blk.c | 86 ++++++++++++++++++++++++++++++++++---- 1 file changed, 78 insertions(+), 8 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 0736248999b0d..d52f33881ab6e 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -32,6 +32,15 @@ struct virtio_blk_vq { } ____cacheline_aligned_in_smp; struct virtio_blk { + /* + * This mutex must be held by anything that may run after + * virtblk_remove() sets vblk->vdev to NULL. + * + * blk-mq, virtqueue processing, and sysfs attribute code paths are + * shut down before vblk->vdev is set to NULL and therefore do not need + * to hold this mutex. + */ + struct mutex vdev_mutex; struct virtio_device *vdev; /* The disk structure for the kernel. */ @@ -43,6 +52,13 @@ struct virtio_blk { /* Process context for config space updates */ struct work_struct config_work; + /* + * Tracks references from block_device_operations open/release and + * virtio_driver probe/remove so this object can be freed once no + * longer in use. + */ + refcount_t refs; + /* What host tells us, plus 2 for header & tailer. */ unsigned int sg_elems; @@ -294,10 +310,55 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str) return err; } +static void virtblk_get(struct virtio_blk *vblk) +{ + refcount_inc(&vblk->refs); +} + +static void virtblk_put(struct virtio_blk *vblk) +{ + if (refcount_dec_and_test(&vblk->refs)) { + ida_simple_remove(&vd_index_ida, vblk->index); + mutex_destroy(&vblk->vdev_mutex); + kfree(vblk); + } +} + +static int virtblk_open(struct block_device *bd, fmode_t mode) +{ + struct virtio_blk *vblk = bd->bd_disk->private_data; + int ret = 0; + + mutex_lock(&vblk->vdev_mutex); + + if (vblk->vdev) + virtblk_get(vblk); + else + ret = -ENXIO; + + mutex_unlock(&vblk->vdev_mutex); + return ret; +} + +static void virtblk_release(struct gendisk *disk, fmode_t mode) +{ + struct virtio_blk *vblk = disk->private_data; + + virtblk_put(vblk); +} + /* We provide getgeo only to please some old bootloader/partitioning tools */ static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo) { struct virtio_blk *vblk = bd->bd_disk->private_data; + int ret = 0; + + mutex_lock(&vblk->vdev_mutex); + + if (!vblk->vdev) { + ret = -ENXIO; + goto out; + } /* see if the host passed in geometry config */ if (virtio_has_feature(vblk->vdev, VIRTIO_BLK_F_GEOMETRY)) { @@ -313,11 +374,15 @@ static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo) geo->sectors = 1 << 5; geo->cylinders = get_capacity(bd->bd_disk) >> 11; } - return 0; +out: + mutex_unlock(&vblk->vdev_mutex); + return ret; } static const struct block_device_operations virtblk_fops = { .owner = THIS_MODULE, + .open = virtblk_open, + .release = virtblk_release, .getgeo = virtblk_getgeo, }; @@ -657,6 +722,10 @@ static int virtblk_probe(struct virtio_device *vdev) goto out_free_index; } + /* This reference is dropped in virtblk_remove(). */ + refcount_set(&vblk->refs, 1); + mutex_init(&vblk->vdev_mutex); + vblk->vdev = vdev; vblk->sg_elems = sg_elems; @@ -822,8 +891,6 @@ static int virtblk_probe(struct virtio_device *vdev) static void virtblk_remove(struct virtio_device *vdev) { struct virtio_blk *vblk = vdev->priv; - int index = vblk->index; - int refc; /* Make sure no work handler is accessing the device. */ flush_work(&vblk->config_work); @@ -833,18 +900,21 @@ static void virtblk_remove(struct virtio_device *vdev) blk_mq_free_tag_set(&vblk->tag_set); + mutex_lock(&vblk->vdev_mutex); + /* Stop all the virtqueues. */ vdev->config->reset(vdev); - refc = kref_read(&disk_to_dev(vblk->disk)->kobj.kref); + /* Virtqueues are stopped, nothing can use vblk->vdev anymore. */ + vblk->vdev = NULL; + put_disk(vblk->disk); vdev->config->del_vqs(vdev); kfree(vblk->vqs); - kfree(vblk); - /* Only free device id if we don't have any users */ - if (refc == 1) - ida_simple_remove(&vd_index_ida, index); + mutex_unlock(&vblk->vdev_mutex); + + virtblk_put(vblk); } #ifdef CONFIG_PM_SLEEP