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>

1 files changed, 6 insertions, 2 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 68383b09c7dc..f9d077d800ee 100644
--- 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;
 }