xenbus: Add proper handling of XS_ERROR from Xenbus for transactions.

If Xenstore sends back a XS_ERROR for TRANSACTION_END, the driver BUGs
because it cannot find the matching transaction in the list.  For
TRANSACTION_START, it leaks memory.

Check the message as returned from xenbus_dev_request_and_reply(), and
clean up for TRANSACTION_START or discard the error for
TRANSACTION_END.

Signed-off-by: Jennifer Herbert <Jennifer.Herbert@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/xen/xenbus/xenbus_dev_frontend.c b/drivers/xen/xenbus/xenbus_dev_frontend.c
index 85534ea63555..9433e46518c8 100644
--- a/drivers/xen/xenbus/xenbus_dev_frontend.c
+++ b/drivers/xen/xenbus/xenbus_dev_frontend.c
@@ -326,10 +326,13 @@ static int xenbus_write_transaction(unsigned msg_type,
         }
 
         if (msg_type == XS_TRANSACTION_START) {
-                trans->handle.id = simple_strtoul(reply, NULL, 0);
-
-                list_add(&trans->list, &u->transactions);
-        } else if (msg_type == XS_TRANSACTION_END) {
+                if (u->u.msg.type == XS_ERROR)
+                        kfree(trans);
+                else {
+                        trans->handle.id = simple_strtoul(reply, NULL, 0);
+                        list_add(&trans->list, &u->transactions);
+                }
+        } else if (u->u.msg.type == XS_TRANSACTION_END) {
                 list_for_each_entry(trans, &u->transactions, list)
                         if (trans->handle.id == u->u.msg.tx_id)
                                 break;