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Drivers: hv: vmbus: serialize process_chn_event() and vmbus_close_internal() 

process_chn_event(), running in the tasklet, can race with
vmbus_close_internal() in the case of SMP guest, e.g., when the former is
accessing channel->inbound.ring_buffer, the latter could be freeing the
ring_buffer pages.

To resolve the race, we can serialize them by disabling the tasklet when
the latter is running here.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dexuan Cui 2015-12-14 16:01:47 -08:00 committed by Greg Kroah-Hartman
parent efc267226b
commit 63d55b2aeb
1 changed files with 19 additions and 2 deletions
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21
drivers/hv/channel.c
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@ -28,6 +28,7 @@
#include <linux/module.h>
#include <linux/hyperv.h>
#include <linux/uio.h>
#include <linux/interrupt.h>
#include "hyperv_vmbus.h"
@ -496,8 +497,21 @@ static void reset_channel_cb(void *arg)
static int vmbus_close_internal(struct vmbus_channel *channel)
{
struct vmbus_channel_close_channel *msg;
struct tasklet_struct *tasklet;
int ret;
/*
* process_chn_event(), running in the tasklet, can race
* with vmbus_close_internal() in the case of SMP guest, e.g., when
* the former is accessing channel->inbound.ring_buffer, the latter
* could be freeing the ring_buffer pages.
*
* To resolve the race, we can serialize them by disabling the
* tasklet when the latter is running here.
*/
tasklet = hv_context.event_dpc[channel->target_cpu];
tasklet_disable(tasklet);
channel->state = CHANNEL_OPEN_STATE;
channel->sc_creation_callback = NULL;
/* Stop callback and cancel the timer asap */
@ -525,7 +539,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
* If we failed to post the close msg,
* it is perhaps better to leak memory.
*/
return ret;
goto out;
}
/* Tear down the gpadl for the channel's ring buffer */
@ -538,7 +552,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
* If we failed to teardown gpadl,
* it is perhaps better to leak memory.
*/
return ret;
goto out;
}
}
@ -555,6 +569,9 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
if (channel->rescind)
hv_process_channel_removal(channel,
channel->offermsg.child_relid);
out:
tasklet_enable(tasklet);
return ret;
}