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Parav Pandit 5715c4dd66 vfio/mdev: Synchronize device create/remove with parent removal 
In following sequences, child devices created while removing mdev parent
device can be left out, or it may lead to race of removing half
initialized child mdev devices.

issue-1:
--------
       cpu-0                         cpu-1
       -----                         -----
                                  mdev_unregister_device()
                                    device_for_each_child()
                                      mdev_device_remove_cb()
                                        mdev_device_remove()
create_store()
  mdev_device_create()                   [...]
    device_add()
                                  parent_remove_sysfs_files()

/* BUG: device added by cpu-0
 * whose parent is getting removed
 * and it won't process this mdev.
 */

issue-2:
--------
Below crash is observed when user initiated remove is in progress
and mdev_unregister_driver() completes parent unregistration.

       cpu-0                         cpu-1
       -----                         -----
remove_store()
   mdev_device_remove()
   active = false;
                                  mdev_unregister_device()
                                  parent device removed.
   [...]
   parents->ops->remove()
 /*
  * BUG: Accessing invalid parent.
  */

This is similar race like create() racing with mdev_unregister_device().

BUG: unable to handle kernel paging request at ffffffffc0585668
PGD e8f618067 P4D e8f618067 PUD e8f61a067 PMD 85adca067 PTE 0
Oops: 0000 [#1] SMP PTI
CPU: 41 PID: 37403 Comm: bash Kdump: loaded Not tainted 5.1.0-rc6-vdevbus+ #6
Hardware name: Supermicro SYS-6028U-TR4+/X10DRU-i+, BIOS 2.0b 08/09/2016
RIP: 0010:mdev_device_remove+0xfa/0x140 [mdev]
Call Trace:
 remove_store+0x71/0x90 [mdev]
 kernfs_fop_write+0x113/0x1a0
 vfs_write+0xad/0x1b0
 ksys_write+0x5a/0xe0
 do_syscall_64+0x5a/0x210
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Therefore, mdev core is improved as below to overcome above issues.

Wait for any ongoing mdev create() and remove() to finish before
unregistering parent device.
This continues to allow multiple create and remove to progress in
parallel for different mdev devices as most common case.
At the same time guard parent removal while parent is being accessed by
create() and remove() callbacks.
create()/remove() and unregister_device() are synchronized by the rwsem.

Refactor device removal code to mdev_device_remove_common() to avoid
acquiring unreg_sem of the parent.

Fixes: 7b96953bc6 ("vfio: Mediated device Core driver")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
 		2019-06-06 12:32:37 -06:00
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accessibility treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 70 2019-05-24 17:36:47 +02:00
acpi Power management fixes for 5.2-rc3 2019-05-31 10:38:35 -07:00
amba treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
android treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
ata treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 209 2019-05-30 11:29:53 -07:00
atm treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
auxdisplay treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
base More power management updates for 5.2-rc1 2019-05-15 08:46:44 -07:00
bcma
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block for-linus-20190601 2019-06-02 09:27:44 -07:00
bluetooth treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
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char treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
clk SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
clocksource treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
connector treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
counter treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
cpufreq treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
cpuidle treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 215 2019-05-30 11:29:54 -07:00
crypto crypto: ux500 - fix license comment syntax error 2019-06-01 18:29:58 +02:00
dax libnvdimm fixes v5.2-rc2 2019-05-25 10:11:23 -07:00
dca treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 33 2019-05-24 17:27:11 +02:00
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firewire treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
firmware Merge branch 'efi-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-06-02 11:06:13 -07:00
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fpga treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
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gpio SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
gpu SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
hid treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 178 2019-05-30 11:29:19 -07:00
hsi treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
hv
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hwmon treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 197 2019-05-30 11:29:22 -07:00
hwspinlock
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hwtracing treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
i2c Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2019-06-02 10:18:11 -07:00
i3c treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
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idle treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
iio SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
infiniband treewide: Add SPDX license identifier - Kbuild 2019-05-30 11:32:33 -07:00
input treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 197 2019-05-30 11:29:22 -07:00
interconnect treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
iommu drivers/iommu/intel-iommu.c: fix variable 'iommu' set but not used 2019-06-01 15:51:32 -07:00
ipack treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
irqchip treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
isdn SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
leds LED fix for 5.2-rc3 2019-06-02 10:14:25 -07:00
lightnvm treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
macintosh treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
mailbox treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
mcb treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
md treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
media SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
memory treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
memstick treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 17 2019-05-21 11:28:46 +02:00
message treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
mfd treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
misc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
mmc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 194 2019-05-30 11:29:22 -07:00
mtd treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
mux
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net SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
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ntb treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
nubus treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
nvdimm libnvdimm fixes v5.2-rc2 2019-05-25 10:11:23 -07:00
nvme for-linus-20190524 2019-05-24 16:02:14 -07:00
nvmem treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
of of_net: Fix missing of_find_device_by_node ref count drop 2019-05-13 08:52:37 -07:00
opp treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
oprofile
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parisc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 217 2019-05-30 11:29:54 -07:00
parport treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
pci PCI: PM: Avoid possible suspend-to-idle issue 2019-05-27 10:55:08 +02:00
pcmcia treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 156 2019-05-30 11:26:35 -07:00
perf treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
phy treewide: fix typos of SPDX-License-Identifier 2019-06-01 18:29:58 +02:00
pinctrl treewide: fix typos of SPDX-License-Identifier 2019-06-01 18:29:58 +02:00
platform treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
pnp treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 150 2019-05-30 11:25:19 -07:00
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powercap treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
pps treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61 2019-05-24 17:36:45 +02:00
ps3 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 167 2019-05-30 11:26:39 -07:00
ptp treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 167 2019-05-30 11:26:39 -07:00
pwm treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 194 2019-05-30 11:29:22 -07:00
rapidio treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
ras treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
regulator treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
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reset treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
rpmsg
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rtc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
s390 SCSI fixes on 20190601 2019-06-02 09:26:34 -07:00
sbus treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61 2019-05-24 17:36:45 +02:00
scsi SCSI fixes on 20190601 2019-06-02 09:26:34 -07:00
sfi treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
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slimbus
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sn treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
soc treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 207 2019-05-30 11:29:53 -07:00
soundwire treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
spi treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
spmi treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
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staging Staging/IIO driver fixes for 5.2-rc3 2019-05-31 08:31:45 -07:00
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tee treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
thermal Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/evalenti/linux-soc-thermal 2019-06-02 10:16:09 -07:00
thunderbolt treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
tty vt/fbcon: deinitialize resources in visual_init() after failed memory allocation 2019-05-24 17:08:18 +02:00
uio treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61 2019-05-24 17:36:45 +02:00
usb usbip: usbip_host: fix stub_dev lock context imbalance regression 2019-05-29 13:26:32 -07:00
uwb treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
vfio vfio/mdev: Synchronize device create/remove with parent removal 2019-06-06 12:32:37 -06:00
vhost treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
video SPDX update for 5.2-rc3, round 1 2019-05-31 08:34:32 -07:00
virt treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
virtio treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 102 2019-05-24 17:39:00 +02:00
visorbus treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
vlynq treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 102 2019-05-24 17:39:00 +02:00
vme treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
w1 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157 2019-05-30 11:26:37 -07:00
watchdog treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206 2019-05-30 11:29:53 -07:00
xen xen: fixes for 5.2-rc3 2019-05-31 10:53:34 -07:00
zorro treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Kconfig
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Makefile
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