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linux/drivers/xen
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Olaf Hering 3366cdb6d3 xen: avoid crash in disable_hotplug_cpu 
The command 'xl vcpu-set 0 0', issued in dom0, will crash dom0:

BUG: unable to handle kernel NULL pointer dereference at 00000000000002d8
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 7 PID: 65 Comm: xenwatch Not tainted 4.19.0-rc2-1.ga9462db-default #1 openSUSE Tumbleweed (unreleased)
Hardware name: Intel Corporation S5520UR/S5520UR, BIOS S5500.86B.01.00.0050.050620101605 05/06/2010
RIP: e030:device_offline+0x9/0xb0
Code: 77 24 00 e9 ce fe ff ff 48 8b 13 e9 68 ff ff ff 48 8b 13 e9 29 ff ff ff 48 8b 13 e9 ea fe ff ff 90 66 66 66 66 90 41 54 55 53 <f6> 87 d8 02 00 00 01 0f 85 88 00 00 00 48 c7 c2 20 09 60 81 31 f6
RSP: e02b:ffffc90040f27e80 EFLAGS: 00010203
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff8801f3800000 RSI: ffffc90040f27e70 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff820e47b3 R09: 0000000000000000
R10: 0000000000007ff0 R11: 0000000000000000 R12: ffffffff822e6d30
R13: dead000000000200 R14: dead000000000100 R15: ffffffff8158b4e0
FS:  00007ffa595158c0(0000) GS:ffff8801f39c0000(0000) knlGS:0000000000000000
CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000002d8 CR3: 00000001d9602000 CR4: 0000000000002660
Call Trace:
 handle_vcpu_hotplug_event+0xb5/0xc0
 xenwatch_thread+0x80/0x140
 ? wait_woken+0x80/0x80
 kthread+0x112/0x130
 ? kthread_create_worker_on_cpu+0x40/0x40
 ret_from_fork+0x3a/0x50

This happens because handle_vcpu_hotplug_event is called twice. In the
first iteration cpu_present is still true, in the second iteration
cpu_present is false which causes get_cpu_device to return NULL.
In case of cpu#0, cpu_online is apparently always true.

Fix this crash by checking if the cpu can be hotplugged, which is false
for a cpu that was just removed.

Also check if the cpu was actually offlined by device_remove, otherwise
leave the cpu_present state as it is.

Rearrange to code to do all work with device_hotplug_lock held.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
2018-09-14 08:51:10 -04:00
..
events xen: Remove unnecessary BUG_ON from __unbind_from_irq() 2018-06-22 08:32:52 +02:00
xen-pciback treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
xenbus xen: export device state to sysfs 2018-08-28 17:37:40 -04:00
xenfs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
acpi.c
arm-device.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
balloon.c xen/balloon: Share common memory reservation routines 2018-07-26 23:05:13 -04:00
biomerge.c xen/biomerge: Use true and false for boolean values 2018-08-06 10:20:57 -04:00
cpu_hotplug.c xen: avoid crash in disable_hotplug_cpu 2018-09-14 08:51:10 -04:00
dbgp.c
efi.c
evtchn.c treewide: kvmalloc() -> kvmalloc_array() 2018-06-12 16:19:22 -07:00
fallback.c
features.c
gntalloc.c mm: treewide: remove GFP_TEMPORARY allocation flag 2017-09-13 18:53:16 -07:00
gntdev-common.h xen/gntdev: Add initial support for dma-buf UAPI 2018-07-26 23:05:14 -04:00
gntdev-dmabuf.c drm pull for 4.19-rc1 2018-08-15 17:39:07 -07:00
gntdev-dmabuf.h xen/gntdev: Add initial support for dma-buf UAPI 2018-07-26 23:05:14 -04:00
gntdev.c mm, oom: distinguish blockable mode for mmu notifiers 2018-08-22 10:52:44 -07:00
grant-table.c xen/grant-table: Allow allocating buffers suitable for DMA 2018-07-26 23:05:14 -04:00
Kconfig xen/balloon: add runtime control for scrubbing ballooned out pages 2018-09-14 08:51:10 -04:00
Makefile xen/gntdev: Add initial support for dma-buf UAPI 2018-07-26 23:05:14 -04:00
manage.c xen/manage: don't complain about an empty value in control/sysrq node 2018-09-14 08:51:10 -04:00
mcelog.c xen/mcelog: eliminate redundant setting of interface version 2018-08-20 14:46:18 -04:00
mem-reservation.c xen/balloon: add runtime control for scrubbing ballooned out pages 2018-09-14 08:51:10 -04:00
pci.c
pcpu.c
platform-pci.c xen-platform: constify pci_device_id. 2017-08-31 09:45:55 -04:00
preempt.c
privcmd-buf.c xen: add new hypercall buffer mapping device 2018-06-22 08:26:42 +02:00
privcmd.c xen: add new hypercall buffer mapping device 2018-06-22 08:26:42 +02:00
privcmd.h xen: add new hypercall buffer mapping device 2018-06-22 08:26:42 +02:00
pvcalls-back.c xen/pvcalls: fix null pointer dereference on map->sock 2018-02-26 17:13:12 +01:00
pvcalls-front.c pvcalls-front: 64-bit align flags 2018-03-01 07:23:36 +01:00
pvcalls-front.h xen: fix poll misannotation 2018-02-01 10:07:32 -05:00
swiotlb-xen.c xen-swiotlb: fix the check condition for xen_swiotlb_free_coherent 2018-05-18 14:37:16 -04:00
sys-hypervisor.c
time.c xen: features and fixes for v4.15-rc1 2017-11-16 13:06:27 -08:00
tmem.c mm, swap, frontswap: fix THP swap if frontswap enabled 2018-02-21 15:35:43 -08:00
xen-acpi-cpuhotplug.c
xen-acpi-memhotplug.c
xen-acpi-pad.c
xen-acpi-processor.c xen/ACPI: don't upload Px/Cx data for disabled processors 2018-08-20 14:46:18 -04:00
xen-balloon.c xen/balloon: add runtime control for scrubbing ballooned out pages 2018-09-14 08:51:10 -04:00
xen-scsiback.c SCSI misc on 20180815 2018-08-15 22:06:26 -07:00
xen-selfballoon.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xen-stub.c
xlate_mmu.c