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| author | Olaf Hering <olaf@aepfle.de> | 2018-09-07 16:31:35 +0200 |
|---|---|---|
| committer | Boris Ostrovsky <boris.ostrovsky@oracle.com> | 2018-09-14 08:51:10 -0400 |
| commit | 3366cdb6d350d95466ee430ac50f3c8415ca8f46 (patch) | |
| tree | 0829fe4e084996f1b505b4b48bcb0aac9057c611 /drivers/xen | |
| parent | 197ecb3802c04499d8ff4f8cb28f6efa008067db (diff) | |
| download | linux-0-day-3366cdb6d350d95466ee430ac50f3c8415ca8f46.tar.gz linux-0-day-3366cdb6d350d95466ee430ac50f3c8415ca8f46.tar.xz | |
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>
Diffstat (limited to 'drivers/xen')
| -rw-r--r-- | drivers/xen/cpu_hotplug.c | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c index d4265c8ebb22a..b1357aa4bc552 100644 --- a/drivers/xen/cpu_hotplug.c +++ b/drivers/xen/cpu_hotplug.c @@ -19,15 +19,16 @@ static void enable_hotplug_cpu(int cpu) static void disable_hotplug_cpu(int cpu) { - if (cpu_online(cpu)) { - lock_device_hotplug(); + if (!cpu_is_hotpluggable(cpu)) + return; + lock_device_hotplug(); + if (cpu_online(cpu)) device_offline(get_cpu_device(cpu)); - unlock_device_hotplug(); - } - if (cpu_present(cpu)) + if (!cpu_online(cpu) && cpu_present(cpu)) { xen_arch_unregister_cpu(cpu); - - set_cpu_present(cpu, false); + set_cpu_present(cpu, false); + } + unlock_device_hotplug(); } static int vcpu_online(unsigned int cpu) |