[PATCH] Drivers: hv: vmbus: Revert commit bb08d431a914

[kys@exchange.microsoft.com]

From: K. Y. Srinivasan <kys@microsoft.com>

To deal with the merge conflict between net-next and char-misc trees,
revert commit bb08d431a914 from char-misc tree. This commit can be rebased
and applied once net-next picks up char-misc changes.
---
 include/linux/hyperv.h |   32 +++++++++++++++++++++-----------
 1 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index c877e79..613074e 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1492,23 +1492,31 @@ static inline struct vmpacket_descriptor *
 get_next_pkt_raw(struct vmbus_channel *channel)
 {
 	struct hv_ring_buffer_info *ring_info = &channel->inbound;
-	u32 priv_read_loc = ring_info->priv_read_index;
+	u32 read_loc = ring_info->priv_read_index;
 	void *ring_buffer = hv_get_ring_buffer(ring_info);
+	struct vmpacket_descriptor *cur_desc;
+	u32 packetlen;
 	u32 dsize = ring_info->ring_datasize;
-	/*
-	 * delta is the difference between what is available to read and
-	 * what was already consumed in place. We commit read index after
-	 * the whole batch is processed.
-	 */
-	u32 delta = priv_read_loc >= ring_info->ring_buffer->read_index ?
-		priv_read_loc - ring_info->ring_buffer->read_index :
-		(dsize - ring_info->ring_buffer->read_index) + priv_read_loc;
+	u32 delta = read_loc - ring_info->ring_buffer->read_index;
 	u32 bytes_avail_toread = (hv_get_bytes_to_read(ring_info) - delta);
 
 	if (bytes_avail_toread < sizeof(struct vmpacket_descriptor))
 		return NULL;
 
-	return ring_buffer + priv_read_loc;
+	if ((read_loc + sizeof(*cur_desc)) > dsize)
+		return NULL;
+
+	cur_desc = ring_buffer + read_loc;
+	packetlen = cur_desc->len8 << 3;
+
+	/*
+	 * If the packet under consideration is wrapping around,
+	 * return failure.
+	 */
+	if ((read_loc + packetlen + VMBUS_PKT_TRAILER) > (dsize - 1))
+		return NULL;
+
+	return cur_desc;
 }
 
 /*
@@ -1520,14 +1528,16 @@ static inline void put_pkt_raw(struct vmbus_channel *channel,
 				struct vmpacket_descriptor *desc)
 {
 	struct hv_ring_buffer_info *ring_info = &channel->inbound;
+	u32 read_loc = ring_info->priv_read_index;
 	u32 packetlen = desc->len8 << 3;
 	u32 dsize = ring_info->ring_datasize;
 
+	if ((read_loc + packetlen + VMBUS_PKT_TRAILER) > dsize)
+		BUG();
 	/*
 	 * Include the packet trailer.
 	 */
 	ring_info->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
-	ring_info->priv_read_index %= dsize;
 }
 
 /*
-- 
1.7.4.1