4.16-stable review patch. If anyone has any objections, please let me know.
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From: Simon Gaiser simon@invisiblethingslab.com
commit 2a22ee6c3ab1d761bc9c04f1e4117edd55b82f09 upstream.
Commit fd8aa9095a95 ("xen: optimize xenbus driver for multiple concurrent xenstore accesses") made a subtle change to the semantic of xenbus_dev_request_and_reply() and xenbus_transaction_end().
Before on an error response to XS_TRANSACTION_END xenbus_dev_request_and_reply() would not decrement the active transaction counter. But xenbus_transaction_end() has always counted the transaction as finished regardless of the response.
The new behavior is that xenbus_dev_request_and_reply() and xenbus_transaction_end() will always count the transaction as finished regardless the response code (handled in xs_request_exit()).
But xenbus_dev_frontend tries to end a transaction on closing of the device if the XS_TRANSACTION_END failed before. Trying to close the transaction twice corrupts the reference count. So fix this by also considering a transaction closed if we have sent XS_TRANSACTION_END once regardless of the return code.
Cc: stable@vger.kernel.org # 4.11 Fixes: fd8aa9095a95 ("xen: optimize xenbus driver for multiple concurrent xenstore accesses") Signed-off-by: Simon Gaiser simon@invisiblethingslab.com Reviewed-by: Juergen Gross jgross@suse.com Signed-off-by: Boris Ostrovsky boris.ostrovsky@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/xen/xenbus/xenbus_dev_frontend.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/xen/xenbus/xenbus_dev_frontend.c +++ b/drivers/xen/xenbus/xenbus_dev_frontend.c @@ -365,7 +365,7 @@ void xenbus_dev_queue_reply(struct xb_re if (WARN_ON(rc)) goto out; } - } else if (req->msg.type == XS_TRANSACTION_END) { + } else if (req->type == XS_TRANSACTION_END) { trans = xenbus_get_transaction(u, req->msg.tx_id); if (WARN_ON(!trans)) goto out;