nfsd: Ensure lookup_clientid() takes client_lock

Ensure that the client lookup is done safely under the client_lock, so
we're not relying on the client_mutex.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 68383b0..f9d077d 100644 (file)
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -3451,13 +3451,17 @@ static __be32 lookup_clientid(clientid_t *clid,
         * will be false.
         */
        WARN_ON_ONCE(cstate->session);
+       spin_lock(&nn->client_lock);
        found = find_confirmed_client(clid, false, nn);
-       if (!found)
+       if (!found) {
+               spin_unlock(&nn->client_lock);
                return nfserr_expired;
+       }
+       atomic_inc(&found->cl_refcount);
+       spin_unlock(&nn->client_lock);
 
        /* Cache the nfs4_client in cstate! */
        cstate->clp = found;
-       atomic_inc(&found->cl_refcount);
        return nfs_ok;
 }