[PATCH 2/4] [for linux-4.4.y only] Drivers: hv: util: Pass the channel information during the init call

[PATCH 2/4] [for linux-4.4.y only] Drivers: hv: util: Pass the channel information during the init call

[Dexuan Cui]

Pass the channel information to the util drivers that need to defer
reading the channel while they are processing a request. This would address
the following issue reported by Vitaly:

Commit 3cace4a61610 ("Drivers: hv: utils: run polling callback always in
interrupt context") removed direct *_transaction.state = HVUTIL_READY
assignments from *_handle_handshake() functions introducing the following
race: if a userspace daemon connects before we get first non-negotiation
request from the server hv_poll_channel() won't set transaction state to
HVUTIL_READY as (!channel) condition will fail, we set it to non-NULL on
the first real request from the server.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
---

This is cherry-picked from the mainline:
b9830d1 ("Drivers: hv: util: Pass the channel information during the init call")

I added my Signed-off-by as I identified and tested the patches.
If this is unnecessary, please feel free to remove it.

 drivers/hv/hv_fcopy.c    | 2 +-
 drivers/hv/hv_kvp.c      | 2 +-
 drivers/hv/hv_snapshot.c | 2 +-
 drivers/hv/hv_util.c     | 1 +
 include/linux/hyperv.h   | 1 +
 5 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
index 12dcbd8..2cce48d 100644
--- a/drivers/hv/hv_fcopy.c
+++ b/drivers/hv/hv_fcopy.c
@@ -256,7 +256,6 @@ void hv_fcopy_onchannelcallback(void *context)
 		 */
 
 		fcopy_transaction.recv_len = recvlen;
-		fcopy_transaction.recv_channel = channel;
 		fcopy_transaction.recv_req_id = requestid;
 		fcopy_transaction.fcopy_msg = fcopy_msg;
 
@@ -323,6 +322,7 @@ static void fcopy_on_reset(void)
 int hv_fcopy_init(struct hv_util_service *srv)
 {
 	recv_buffer = srv->recv_buffer;
+	fcopy_transaction.recv_channel = srv->channel;
 
 	init_completion(&release_event);
 	/*
diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
index b97ef3e..cd3fb01 100644
--- a/drivers/hv/hv_kvp.c
+++ b/drivers/hv/hv_kvp.c
@@ -640,7 +640,6 @@ void hv_kvp_onchannelcallback(void *context)
 			 */
 
 			kvp_transaction.recv_len = recvlen;
-			kvp_transaction.recv_channel = channel;
 			kvp_transaction.recv_req_id = requestid;
 			kvp_transaction.kvp_msg = kvp_msg;
 
@@ -690,6 +689,7 @@ int
 hv_kvp_init(struct hv_util_service *srv)
 {
 	recv_buffer = srv->recv_buffer;
+	kvp_transaction.recv_channel = srv->channel;
 
 	init_completion(&release_event);
 	/*
diff --git a/drivers/hv/hv_snapshot.c b/drivers/hv/hv_snapshot.c
index c5fb249..b0feddb 100644
--- a/drivers/hv/hv_snapshot.c
+++ b/drivers/hv/hv_snapshot.c
@@ -264,7 +264,6 @@ void hv_vss_onchannelcallback(void *context)
 			 */
 
 			vss_transaction.recv_len = recvlen;
-			vss_transaction.recv_channel = channel;
 			vss_transaction.recv_req_id = requestid;
 			vss_transaction.msg = (struct hv_vss_msg *)vss_msg;
 
@@ -340,6 +339,7 @@ hv_vss_init(struct hv_util_service *srv)
 		return -ENOTSUPP;
 	}
 	recv_buffer = srv->recv_buffer;
+	vss_transaction.recv_channel = srv->channel;
 
 	/*
 	 * When this driver loads, the user level daemon that
diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index 41f5896..9dc6372 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -326,6 +326,7 @@ static int util_probe(struct hv_device *dev,
 	srv->recv_buffer = kmalloc(PAGE_SIZE * 4, GFP_KERNEL);
 	if (!srv->recv_buffer)
 		return -ENOMEM;
+	srv->channel = dev->channel;
 	if (srv->util_init) {
 		ret = srv->util_init(srv);
 		if (ret) {
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index ae6a711..281bb00 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1179,6 +1179,7 @@ int vmbus_allocate_mmio(struct resource **new, struct hv_device *device_obj,
 
 struct hv_util_service {
 	u8 *recv_buffer;
+	void *channel;
 	void (*util_cb)(void *);
 	int (*util_init)(struct hv_util_service *);
 	void (*util_deinit)(void);
-- 
2.7.4