NFSv4.1: protect destroying and nullifying bc_serv structure

When we are shutting down the client, we free the callback
server structure and then at a later pointer we free the
transport used by the client. Yet, it's possible that after
the callback server is freed, the transport receives a
backchannel request at which point we can dereferene freed
memory. Instead, do the freeing the bc server and nullying
bc_serv under the lock.

Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index 8b674ee093a6065df7f1fce15068a85742371cb8..fabda0f6ec1a8ab1017553b755693a4a371f578d 100644 (file)
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -270,7 +270,7 @@ void nfs_callback_down(int minorversion, struct net *net, struct rpc_xprt *xprt)
        if (cb_info->users == 0) {
                svc_set_num_threads(serv, NULL, 0);
                dprintk("nfs_callback_down: service destroyed\n");
-               svc_destroy(&cb_info->serv);
+               xprt_svc_destroy_nullify_bc(xprt, &cb_info->serv);
        }
        mutex_unlock(&nfs_callback_mutex);
 }