xen: xenbus: Catch closing of non existent transactions

Users of the xenbus functions should never close a non existent
transaction (for example by trying to closing the same transaction
twice) but better catch it in xs_request_exit() than to corrupt the
reference counter.

Signed-off-by: Simon Gaiser <simon@invisiblethingslab.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 3f3b29398ab8..49a3874ae6bb 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -140,7 +140,9 @@ void xs_request_exit(struct xb_req_data *req)
         spin_lock(&xs_state_lock);
         xs_state_users--;
         if ((req->type == XS_TRANSACTION_START && req->msg.type == XS_ERROR) ||
-            req->type == XS_TRANSACTION_END)
+            (req->type == XS_TRANSACTION_END &&
+             !WARN_ON_ONCE(req->msg.type == XS_ERROR &&
+                           !strcmp(req->body, "ENOENT"))))
                 xs_state_users--;
         spin_unlock(&xs_state_lock);