nfsd: restore callback functionality for NFSv4.0

A recent patch inadvertently broke callbacks for NFSv4.0.

In the 4.0 case we do not expect a session to be found but still need to
call setup_callback_client() which will not try to dereference it.

This patch moves the check for failure to find a session into the 4.1+
branch of setup_callback_client()

Fixes: 1e02c641c3a4 ("NFSD: Prevent NULL dereference in nfsd4_process_cb_update()")
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 3877b53e429fd89899d7dc35086bee8bda6eed07..c083e539e898ba6593bc0d6185ccb8692aae6a95 100644 (file)
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -1100,7 +1100,7 @@ static int setup_callback_client(struct nfs4_client *clp, struct nfs4_cb_conn *c
                args.authflavor = clp->cl_cred.cr_flavor;
                clp->cl_cb_ident = conn->cb_ident;
        } else {
-               if (!conn->cb_xprt)
+               if (!conn->cb_xprt || !ses)
                        return -EINVAL;
                clp->cl_cb_session = ses;
                args.bc_xprt = conn->cb_xprt;
@@ -1522,8 +1522,6 @@ static void nfsd4_process_cb_update(struct nfsd4_callback *cb)
                ses = c->cn_session;
        }
        spin_unlock(&clp->cl_lock);
-       if (!c)
-               return;
 
        err = setup_callback_client(clp, &conn, ses);
        if (err) {