hv: acquire vmbus_connection.channel_mutex in vmbus_free_channels()

"kernel BUG at drivers/hv/channel_mgmt.c:350!" is observed when hv_vmbus
module is unloaded. BUG_ON() was introduced in commit 85d9aa705184
("Drivers: hv: vmbus: add an API vmbus_hvsock_device_unregister()") as
vmbus_free_channels() codepath was apparently forgotten.

Fixes: 85d9aa705184 ("Drivers: hv: vmbus: add an API vmbus_hvsock_device_unregister()")

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index e5d1b0e6c922..26b419203f16 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -389,6 +389,7 @@ void vmbus_free_channels(void)
 {
         struct vmbus_channel *channel, *tmp;
 
+        mutex_lock(&vmbus_connection.channel_mutex);
         list_for_each_entry_safe(channel, tmp, &vmbus_connection.chn_list,
                 listentry) {
                 /* hv_process_channel_removal() needs this */
@@ -396,6 +397,7 @@ void vmbus_free_channels(void)
 
                 vmbus_device_unregister(channel->device_obj);
         }
+        mutex_unlock(&vmbus_connection.channel_mutex);
 }
 
 /*