NFSv4: Fix NFSv4 reference counting for trunked sessions

The reference counting in nfs4_init_client assumes wongly that it
is safe for nfs4_discover_server_trunking() to return a pointer to a
nfs_client prior to bumping the reference count.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ben Greear <greearb@candelatech.com>
Cc: stable@vger.kernel.org [>=3.7]

diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index acc3472..65a290a 100644 (file)
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -236,11 +236,10 @@ struct nfs_client *nfs4_init_client(struct nfs_client *clp,
        error = nfs4_discover_server_trunking(clp, &old);
        if (error < 0)
                goto error;
+       nfs_put_client(clp);
        if (clp != old) {
                clp->cl_preserve_clid = true;
-               nfs_put_client(clp);
                clp = old;
-               atomic_inc(&clp->cl_count);
        }
 
        return clp;
@@ -306,7 +305,7 @@ int nfs40_walk_client_list(struct nfs_client *new,
                .clientid       = new->cl_clientid,
                .confirm        = new->cl_confirm,
        };
-       int status;
+       int status = -NFS4ERR_STALE_CLIENTID;
 
        spin_lock(&nn->nfs_client_lock);
        list_for_each_entry_safe(pos, n, &nn->nfs_client_list, cl_share_link) {
@@ -332,28 +331,28 @@ int nfs40_walk_client_list(struct nfs_client *new,
 
                if (prev)
                        nfs_put_client(prev);
+               prev = pos;
 
                status = nfs4_proc_setclientid_confirm(pos, &clid, cred);
-               if (status == 0) {
+               switch (status) {
+               case -NFS4ERR_STALE_CLIENTID:
+                       break;
+               case 0:
                        nfs4_swap_callback_idents(pos, new);
 
-                       nfs_put_client(pos);
+                       prev = NULL;
                        *result = pos;
                        dprintk("NFS: <-- %s using nfs_client = %p ({%d})\n",
                                __func__, pos, atomic_read(&pos->cl_count));
-                       return 0;
-               }
-               if (status != -NFS4ERR_STALE_CLIENTID) {
-                       nfs_put_client(pos);
-                       dprintk("NFS: <-- %s status = %d, no result\n",
-                               __func__, status);
-                       return status;
+               default:
+                       goto out;
                }
 
                spin_lock(&nn->nfs_client_lock);
-               prev = pos;
        }
+       spin_unlock(&nn->nfs_client_lock);
 
+out:
        /*
         * No matching nfs_client found.  This should be impossible,
         * because the new nfs_client has already been added to
@@ -363,9 +362,8 @@ int nfs40_walk_client_list(struct nfs_client *new,
         */
        if (prev)
                nfs_put_client(prev);
-       spin_unlock(&nn->nfs_client_lock);
-       pr_err("NFS: %s Error: no matching nfs_client found\n", __func__);
-       return -NFS4ERR_STALE_CLIENTID;
+       dprintk("NFS: <-- %s status = %d\n", __func__, status);
+       return status;
 }
 
 #ifdef CONFIG_NFS_V4_1
@@ -473,6 +471,7 @@ int nfs41_walk_client_list(struct nfs_client *new,
                if (!nfs4_match_serverowners(pos, new))
                        continue;
 
+               atomic_inc(&pos->cl_count);
                spin_unlock(&nn->nfs_client_lock);
                dprintk("NFS: <-- %s using nfs_client = %p ({%d})\n",
                        __func__, pos, atomic_read(&pos->cl_count));