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Stefan Hajnoczi 90b5feb8c4 virtio-blk: handle block_device_operations callbacks after hot unplug
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: [<ffffffffc00e5450>] 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:[<ffffffffc00e5450>]  [<ffffffffc00e5450>] 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:
   [<ffffffffc016ac37>] virtblk_getgeo+0x47/0x110 [virtio_blk]
   [<ffffffff8d3f200d>] ? handle_mm_fault+0x39d/0x9b0
   [<ffffffff8d561265>] blkdev_ioctl+0x1f5/0xa20
   [<ffffffff8d488771>] block_ioctl+0x41/0x50
   [<ffffffff8d45d9e0>] do_vfs_ioctl+0x3a0/0x5a0
   [<ffffffff8d45dc81>] 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: 48e4043d45 ("virtio: add virtio disk geometry feature")
Reported-by: Lance Digby <ldigby@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Link: https://lore.kernel.org/r/20200430140442.171016-1-stefanha@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
2020-05-02 10:28:13 -04:00
arch s390 fixes for 5.7-rc3 2020-04-26 10:58:49 -07:00
block blk-iocost: Fix error on iocost_ioc_vrate_adj 2020-04-21 09:49:36 -06:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-04-01 14:47:40 -07:00
Documentation USB fixes for 5.7-rc3 2020-04-26 11:22:01 -07:00
drivers virtio-blk: handle block_device_operations callbacks after hot unplug 2020-05-02 10:28:13 -04:00
fs Five cifs/smb3 fixes, 3 for DFS, one for stable 2020-04-26 11:44:17 -07:00
include Staging/IIO driver fixes for 5.7-rc3 2020-04-26 11:12:30 -07:00
init Kbuild updates for v5.7 (2nd) 2020-04-11 09:46:12 -07:00
ipc ipc/util.c: sysvipc_find_ipc() should increase position index 2020-04-10 15:36:22 -07:00
kernel Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2020-04-25 12:25:32 -07:00
lib lib/mpi: Fix building for powerpc with clang 2020-04-24 13:14:59 +10:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm: check that mm is still valid in madvise() 2020-04-24 13:28:03 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-04-24 19:17:30 -07:00
samples vmalloc: fix remap_vmalloc_range() bounds checks 2020-04-21 11:11:56 -07:00
scripts Kbuild fixes for v5.7 2020-04-24 10:39:32 -07:00
security selinux/stable-5.7 PR 20200416 2020-04-16 10:45:47 -07:00
sound sound fixes for 5.7-rc3 2020-04-24 10:27:43 -07:00
tools Two fixes: fix an off-by-one bug, and fix 32-bit builds on 64-bit systems. 2020-04-25 11:52:02 -07:00
usr kbuild: fix comment about missing include guard detection 2020-04-11 12:09:48 +09:00
virt KVM: Pass kvm_init()'s opaque param to additional arch funcs 2020-03-31 10:48:03 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2020-04-18 13:49:33 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
.mailmap mailmap: Add Sedat Dilek (replacement for expired email address) 2020-04-11 09:28:34 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Hand MIPS over to Thomas 2020-02-24 22:43:18 -08:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Staging/IIO driver fixes for 5.7-rc3 2020-04-26 11:12:30 -07:00
Makefile Linux 5.7-rc3 2020-04-26 13:51:02 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.