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Commit 8b5d6d3b authored by Haiyang Zhang's avatar Haiyang Zhang Committed by Greg Kroah-Hartman
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staging: hv: Fix race condition on vmbus channel initialization 



There is a possible race condition when hv_utils starts to load immediately
after hv_vmbus is loading - null pointer error could happen.
This patch added wait/completion to ensure all channels are ready before
vmbus loading completes. So another module won't have any uninitialized channel.

Signed-off-by: default avatarHaiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: default avatarHank Janssen <hjanssen@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 6c2fd308

drivers/staging/hv/channel_mgmt.c

+30 −11
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/slab.h>

#include <linux/list.h>

#include <linux/module.h>

#include <linux/completion.h>

#include "osd.h"

#include "logging.h"

#include "vmbus_private.h"
@@ -293,6 +294,25 @@ void FreeVmbusChannel(struct vmbus_channel *Channel) 
			      Channel);

}





DECLARE_COMPLETION(hv_channel_ready);



/*

 * Count initialized channels, and ensure all channels are ready when hv_vmbus

 * module loading completes.

 */

static void count_hv_channel(void)

{

	static int counter;

	unsigned long flags;



	spin_lock_irqsave(&gVmbusConnection.channel_lock, flags);

	if (++counter == MAX_MSG_TYPES)

		complete(&hv_channel_ready);

	spin_unlock_irqrestore(&gVmbusConnection.channel_lock, flags);

}





/*

 * VmbusChannelProcessOffer - Process the offer by creating a channel/device

 * associated with this offer
@@ -373,22 +393,21 @@ static void VmbusChannelProcessOffer(void *context) 
		 * can cleanup properly

		 */

		newChannel->State = CHANNEL_OPEN_STATE;

		cnt = 0;



		while (cnt != MAX_MSG_TYPES) {

		/* Open IC channels */

		for (cnt = 0; cnt < MAX_MSG_TYPES; cnt++) {

			if (memcmp(&newChannel->OfferMsg.Offer.InterfaceType,

				   &hv_cb_utils[cnt].data,

				   sizeof(struct hv_guid)) == 0) {

				DPRINT_INFO(VMBUS, "%s",

					    hv_cb_utils[cnt].log_msg);



				if (VmbusChannelOpen(newChannel, 2 * PAGE_SIZE,

				   sizeof(struct hv_guid)) == 0 &&

				VmbusChannelOpen(newChannel, 2 * PAGE_SIZE,

						 2 * PAGE_SIZE, NULL, 0,

						 hv_cb_utils[cnt].callback,

						    newChannel) == 0)

						 newChannel) == 0) {

				hv_cb_utils[cnt].channel = newChannel;

				DPRINT_INFO(VMBUS, "%s",

						hv_cb_utils[cnt].log_msg);

				count_hv_channel();

			}

			cnt++;

		}

	}

	DPRINT_EXIT(VMBUS);

drivers/staging/hv/vmbus.h

+2 −0
Original line number Diff line number Diff line
@@ -74,4 +74,6 @@ int vmbus_child_driver_register(struct driver_context *driver_ctx); 
void vmbus_child_driver_unregister(struct driver_context *driver_ctx);

void vmbus_get_interface(struct vmbus_channel_interface *interface);



extern struct completion hv_channel_ready;



#endif /* _VMBUS_H_ */

drivers/staging/hv/vmbus_drv.c

+3 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
#include <linux/pci.h>

#include <linux/dmi.h>

#include <linux/slab.h>

#include <linux/completion.h>

#include "version_info.h"

#include "osd.h"

#include "logging.h"
@@ -356,6 +357,8 @@ static int vmbus_bus_init(int (*drv_init)(struct hv_driver *drv)) 


	vmbus_drv_obj->GetChannelOffers();



	wait_for_completion(&hv_channel_ready);



cleanup:

	DPRINT_EXIT(VMBUS_DRV);