Three bug fixes for different parts of the hyper-v code:

- Fix for a lockup when changing NIC's MTU from Dexuan.
  - Fix of use of uninitialized memory from Dexuan.
  - Fix for memory corruption caused by ballooning from Vitaly.
 
 All 3 were tested internally.
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Merge tag 'hyperv-fixes-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux into char-misc-linus

Sasha writes:

Three bug fixes for different parts of the hyper-v code:

 - Fix for a lockup when changing NIC's MTU from Dexuan.
 - Fix of use of uninitialized memory from Dexuan.
 - Fix for memory corruption caused by ballooning from Vitaly.

All 3 were tested internally.

* tag 'hyperv-fixes-signed' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux:
  vmbus: fix subchannel removal
  hv_balloon: avoid touching uninitialized struct page during tail onlining
  Drivers: hv: vmbus: Check for ring when getting debug info

drivers/hv/channel.c

@@ -701,19 +701,12 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
 int vmbus_disconnect_ring(struct vmbus_channel *channel)
 {
 	struct vmbus_channel *cur_channel, *tmp;
-	unsigned long flags;
-	LIST_HEAD(list);
 	int ret;
 
 	if (channel->primary_channel != NULL)
 		return -EINVAL;
 
-	/* Snapshot the list of subchannels */
-	spin_lock_irqsave(&channel->lock, flags);
-	list_splice_init(&channel->sc_list, &list);
-	spin_unlock_irqrestore(&channel->lock, flags);
-
-	list_for_each_entry_safe(cur_channel, tmp, &list, sc_list) {
+	list_for_each_entry_safe(cur_channel, tmp, &channel->sc_list, sc_list) {
 		if (cur_channel->rescind)
 			wait_for_completion(&cur_channel->rescind_event);
 

drivers/hv/hv_balloon.c

@@ -888,12 +888,14 @@ static unsigned long handle_pg_range(unsigned long pg_start,
 			pfn_cnt -= pgs_ol;
 			/*
 			 * Check if the corresponding memory block is already
-			 * online by checking its last previously backed page.
-			 * In case it is we need to bring rest (which was not
-			 * backed previously) online too.
+			 * online. It is possible to observe struct pages still
+			 * being uninitialized here so check section instead.
+			 * In case the section is online we need to bring the
+			 * rest of pfns (which were not backed previously)
+			 * online too.
 			 */
 			if (start_pfn > has->start_pfn &&
-			    !PageReserved(pfn_to_page(start_pfn - 1)))
+			    online_section_nr(pfn_to_section_nr(start_pfn)))
 				hv_bring_pgs_online(has, start_pfn, pgs_ol);
 
 		}

drivers/hv/ring_buffer.c

@@ -164,26 +164,25 @@ hv_get_ringbuffer_availbytes(const struct hv_ring_buffer_info *rbi,
 }
 
 /* Get various debug metrics for the specified ring buffer. */
-void hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info,
-				 struct hv_ring_buffer_debug_info *debug_info)
+int hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info,
+				struct hv_ring_buffer_debug_info *debug_info)
 {
 	u32 bytes_avail_towrite;
 	u32 bytes_avail_toread;
 
-	if (ring_info->ring_buffer) {
-		hv_get_ringbuffer_availbytes(ring_info,
-					&bytes_avail_toread,
-					&bytes_avail_towrite);
+	if (!ring_info->ring_buffer)
+		return -EINVAL;
 
-		debug_info->bytes_avail_toread = bytes_avail_toread;
-		debug_info->bytes_avail_towrite = bytes_avail_towrite;
-		debug_info->current_read_index =
-			ring_info->ring_buffer->read_index;
-		debug_info->current_write_index =
-			ring_info->ring_buffer->write_index;
-		debug_info->current_interrupt_mask =
-			ring_info->ring_buffer->interrupt_mask;
-	}
+	hv_get_ringbuffer_availbytes(ring_info,
+				     &bytes_avail_toread,
+				     &bytes_avail_towrite);
+	debug_info->bytes_avail_toread = bytes_avail_toread;
+	debug_info->bytes_avail_towrite = bytes_avail_towrite;
+	debug_info->current_read_index = ring_info->ring_buffer->read_index;
+	debug_info->current_write_index = ring_info->ring_buffer->write_index;
+	debug_info->current_interrupt_mask
+		= ring_info->ring_buffer->interrupt_mask;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(hv_ringbuffer_get_debuginfo);
 

drivers/hv/vmbus_drv.c

@@ -313,12 +313,16 @@ static ssize_t out_intr_mask_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info outbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
+					  &outbound);
+	if (ret < 0)
+		return ret;
+
 	return sprintf(buf, "%d\n", outbound.current_interrupt_mask);
 }
 static DEVICE_ATTR_RO(out_intr_mask);
@@ -328,12 +332,15 @@ static ssize_t out_read_index_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info outbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
+					  &outbound);
+	if (ret < 0)
+		return ret;
 	return sprintf(buf, "%d\n", outbound.current_read_index);
 }
 static DEVICE_ATTR_RO(out_read_index);
@@ -344,12 +351,15 @@ static ssize_t out_write_index_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info outbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
+					  &outbound);
+	if (ret < 0)
+		return ret;
 	return sprintf(buf, "%d\n", outbound.current_write_index);
 }
 static DEVICE_ATTR_RO(out_write_index);
@@ -360,12 +370,15 @@ static ssize_t out_read_bytes_avail_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info outbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
+					  &outbound);
+	if (ret < 0)
+		return ret;
 	return sprintf(buf, "%d\n", outbound.bytes_avail_toread);
 }
 static DEVICE_ATTR_RO(out_read_bytes_avail);
@@ -376,12 +389,15 @@ static ssize_t out_write_bytes_avail_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info outbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound, &outbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->outbound,
+					  &outbound);
+	if (ret < 0)
+		return ret;
 	return sprintf(buf, "%d\n", outbound.bytes_avail_towrite);
 }
 static DEVICE_ATTR_RO(out_write_bytes_avail);
@@ -391,12 +407,15 @@ static ssize_t in_intr_mask_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info inbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+	if (ret < 0)
+		return ret;
+
 	return sprintf(buf, "%d\n", inbound.current_interrupt_mask);
 }
 static DEVICE_ATTR_RO(in_intr_mask);
@@ -406,12 +425,15 @@ static ssize_t in_read_index_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info inbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+	if (ret < 0)
+		return ret;
+
 	return sprintf(buf, "%d\n", inbound.current_read_index);
 }
 static DEVICE_ATTR_RO(in_read_index);
@@ -421,12 +443,15 @@ static ssize_t in_write_index_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info inbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+	if (ret < 0)
+		return ret;
+
 	return sprintf(buf, "%d\n", inbound.current_write_index);
 }
 static DEVICE_ATTR_RO(in_write_index);
@@ -437,12 +462,15 @@ static ssize_t in_read_bytes_avail_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info inbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+	if (ret < 0)
+		return ret;
+
 	return sprintf(buf, "%d\n", inbound.bytes_avail_toread);
 }
 static DEVICE_ATTR_RO(in_read_bytes_avail);
@@ -453,12 +481,15 @@ static ssize_t in_write_bytes_avail_show(struct device *dev,
 {
 	struct hv_device *hv_dev = device_to_hv_device(dev);
 	struct hv_ring_buffer_debug_info inbound;
+	int ret;
 
 	if (!hv_dev->channel)
 		return -ENODEV;
-	if (hv_dev->channel->state != CHANNEL_OPENED_STATE)
-		return -EINVAL;
-	hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+
+	ret = hv_ringbuffer_get_debuginfo(&hv_dev->channel->inbound, &inbound);
+	if (ret < 0)
+		return ret;
+
 	return sprintf(buf, "%d\n", inbound.bytes_avail_towrite);
 }
 static DEVICE_ATTR_RO(in_write_bytes_avail);

include/linux/hyperv.h

@@ -1159,8 +1159,9 @@ struct hv_ring_buffer_debug_info {
 	u32 bytes_avail_towrite;
 };
 
-void hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info,
-			    struct hv_ring_buffer_debug_info *debug_info);
+
+int hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info,
+				struct hv_ring_buffer_debug_info *debug_info);
 
 /* Vmbus interface */
 #define vmbus_driver_register(driver)	\