Re: [PATCH 1/1] Drivers: hv: vmbus: Close timing hole that can corrupt per-cpu page Extend the disabling of preemption to include the hypercall so that another thread can't get the CPU and corrupt the per-cpu page used for hypercall arguments.
From: Joshua R. Poulson
Date: Wed May 17 2017 - 18:05:21 EST
This looks like a bugfix that should be included in stable.
On Wed, May 17, 2017 at 3:00 PM, Stephen Hemminger
> On Wed, 17 May 2017 14:40:55 -0700
> mikelley@xxxxxxxxxxxxxxxxxxxxxx wrote:
>> From: Michael Kelley <mikelley@xxxxxxxxxxxxx>
>> Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
>> drivers/hv/hv.c | 7 ++++++-
>> 1 files changed, 6 insertions(+), 1 deletions(-)
>> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
>> index 12e7bae..47ed538 100644
>> --- a/drivers/hv/hv.c
>> +++ b/drivers/hv/hv.c
>> @@ -82,9 +82,14 @@ int hv_post_message(union hv_connection_id connection_id,
>> aligned_msg->message_type = message_type;
>> aligned_msg->payload_size = payload_size;
>> memcpy((void *)aligned_msg->payload, payload, payload_size);
>> - put_cpu_ptr(hv_cpu);
>> status = hv_do_hypercall(HVCALL_POST_MESSAGE, aligned_msg, NULL);
>> + /* Preemption must remain disabled until after the hypercall
>> + * so some other thread can't get scheduled onto this cpu and
>> + * corrupt the per-cpu post_msg_page
>> + */
>> + put_cpu_ptr(hv_cpu);
>> return status & 0xFFFF;
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