From: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Subject: [PATCH 1/2] staging: hv: Fix race condition in hv_utils module 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 an atomic counter to ensure the hv_utils module initialization
happens after all vmbus IC channels are initialized.
Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Signed-off-by: Hank Janssen <hjanssen@xxxxxxxxxxxxx>
---
drivers/staging/hv/channel_mgmt.c | 26 +++++++++++++++-----------
drivers/staging/hv/hv_utils.c | 11 ++++++++---
drivers/staging/hv/utils.h | 5 +++++
3 files changed, 28 insertions(+), 14 deletions(-)
diff --git a/drivers/staging/hv/channel_mgmt.c b/drivers/staging/hv/channel_mgmt.c
index 3f53b4d..b5b6a70 100644
--- a/drivers/staging/hv/channel_mgmt.c
+++ b/drivers/staging/hv/channel_mgmt.c
@@ -33,7 +33,6 @@ struct vmbus_channel_message_table_entry {
void (*messageHandler)(struct vmbus_channel_message_header *msg);
};
-#define MAX_MSG_TYPES 3
#define MAX_NUM_DEVICE_CLASSES_SUPPORTED 7
static const struct hv_guid
@@ -233,6 +232,11 @@ struct hyperv_service_callback hv_cb_utils[MAX_MSG_TYPES] = {
};
EXPORT_SYMBOL(hv_cb_utils);
+/* Counter of IC channels initialized */
+atomic_t hv_utils_initcnt = ATOMIC_INIT(0);
+EXPORT_SYMBOL(hv_utils_initcnt);
+
+
/*
* AllocVmbusChannel - Allocate and initialize a vmbus channel object
*/
@@ -373,22 +377,22 @@ 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;
+ mb();
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;
+ atomic_inc(&hv_utils_initcnt);
}
- cnt++;
}
}
DPRINT_EXIT(VMBUS);
diff --git a/drivers/staging/hv/hv_utils.c b/drivers/staging/hv/hv_utils.c
index 8a49aaf..f9826c7 100644
--- a/drivers/staging/hv/hv_utils.c
+++ b/drivers/staging/hv/hv_utils.c
@@ -253,7 +253,11 @@ static void heartbeat_onchannelcallback(void *context)
static int __init init_hyperv_utils(void)
{
- printk(KERN_INFO "Registering HyperV Utility Driver\n");
+ printk(KERN_INFO "Registering HyperV Utility Driver...\n");
+
+ /* Wait until all IC channels are initialized */
+ while (atomic_read(&hv_utils_initcnt) < MAX_MSG_TYPES)
+ msleep(100);
hv_cb_utils[HV_SHUTDOWN_MSG].channel->OnChannelCallback =
&shutdown_onchannelcallback;
@@ -267,13 +271,12 @@ static int __init init_hyperv_utils(void)
&heartbeat_onchannelcallback;
hv_cb_utils[HV_HEARTBEAT_MSG].callback = &heartbeat_onchannelcallback;
+ printk(KERN_INFO "Registered HyperV Utility Driver.\n");
return 0;
}
static void exit_hyperv_utils(void)
{
- printk(KERN_INFO "De-Registered HyperV Utility Driver\n");
-
hv_cb_utils[HV_SHUTDOWN_MSG].channel->OnChannelCallback =
&chn_cb_negotiate;
hv_cb_utils[HV_SHUTDOWN_MSG].callback = &chn_cb_negotiate;
@@ -285,6 +288,8 @@ static void exit_hyperv_utils(void)
hv_cb_utils[HV_HEARTBEAT_MSG].channel->OnChannelCallback =
&chn_cb_negotiate;
hv_cb_utils[HV_HEARTBEAT_MSG].callback = &chn_cb_negotiate;
+
+ printk(KERN_INFO "De-Registered HyperV Utility Driver.\n");
}
module_init(init_hyperv_utils);
diff --git a/drivers/staging/hv/utils.h b/drivers/staging/hv/utils.h
index 7c07499..3291ab4 100644
--- a/drivers/staging/hv/utils.h
+++ b/drivers/staging/hv/utils.h
@@ -98,6 +98,10 @@ struct ictimesync_data{
u8 flags;
} __attribute__((packed));
+
+/* Number of IC types supported */
+#define MAX_MSG_TYPES 3
+
/* Index for each IC struct in array hv_cb_utils[] */
#define HV_SHUTDOWN_MSG 0
#define HV_TIMESYNC_MSG 1
@@ -115,5 +119,6 @@ extern void prep_negotiate_resp(struct icmsg_hdr *,
struct icmsg_negotiate *, u8 *);
extern void chn_cb_negotiate(void *);
extern struct hyperv_service_callback hv_cb_utils[];
+extern atomic_t hv_utils_initcnt;
#endif /* __HV_UTILS_H_ */
--
1.6.3.2
Attachment:
0518-1-Fix-race-condition-in-hv_utils-module-initialization.patch
Description: 0518-1-Fix-race-condition-in-hv_utils-module-initialization.patch
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