From: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Subject: [PATCH] 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: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Signed-off-by: Hank Janssen <hjanssen@xxxxxxxxxxxxx>
---
drivers/staging/hv/channel_mgmt.c | 41 +++++++++++++++++++++++++++----------
drivers/staging/hv/vmbus.h | 2 +
drivers/staging/hv/vmbus_drv.c | 3 ++
3 files changed, 35 insertions(+), 11 deletions(-)
diff --git a/drivers/staging/hv/channel_mgmt.c b/drivers/staging/hv/channel_mgmt.c
index 3f53b4d..12db555 100644
--- a/drivers/staging/hv/channel_mgmt.c
+++ b/drivers/staging/hv/channel_mgmt.c
@@ -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) {
+ sizeof(struct hv_guid)) == 0 &&
+ VmbusChannelOpen(newChannel, 2 * PAGE_SIZE,
+ 2 * PAGE_SIZE, NULL, 0,
+ hv_cb_utils[cnt].callback,
+ newChannel) == 0) {
+ hv_cb_utils[cnt].channel = newChannel;
DPRINT_INFO(VMBUS, "%s",
- hv_cb_utils[cnt].log_msg);
-
- if (VmbusChannelOpen(newChannel, 2 * PAGE_SIZE,
- 2 * PAGE_SIZE, NULL, 0,
- hv_cb_utils[cnt].callback,
- newChannel) == 0)
- hv_cb_utils[cnt].channel = newChannel;
+ hv_cb_utils[cnt].log_msg);
+ count_hv_channel();
}
- cnt++;
}
}
DPRINT_EXIT(VMBUS);
diff --git a/drivers/staging/hv/vmbus.h b/drivers/staging/hv/vmbus.h
index 0c6ee0f..3c14b29 100644
--- a/drivers/staging/hv/vmbus.h
+++ b/drivers/staging/hv/vmbus.h
@@ -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_ */
diff --git a/drivers/staging/hv/vmbus_drv.c b/drivers/staging/hv/vmbus_drv.c
index c21731a..22c80ec 100644
--- a/drivers/staging/hv/vmbus_drv.c
+++ b/drivers/staging/hv/vmbus_drv.c
@@ -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);
--
1.6.3.2
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