nfs4: start callback_ident at idr 1

If clp->cl_cb_ident is zero, then nfs_cb_idr_remove_locked() skips removing
it when the nfs_client is freed.  A decoding or server bug can then find
and try to put that first nfs_client which would lead to a crash.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Fixes: d6870312659d ("nfs4client: convert to idr_alloc()")
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index 223bedd..10410e8 100644 (file)
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -33,7 +33,7 @@ static int nfs_get_cb_ident_idr(struct nfs_client *clp, int minorversion)
                return ret;
        idr_preload(GFP_KERNEL);
        spin_lock(&nn->nfs_client_lock);
-       ret = idr_alloc(&nn->cb_ident_idr, clp, 0, 0, GFP_NOWAIT);
+       ret = idr_alloc(&nn->cb_ident_idr, clp, 1, 0, GFP_NOWAIT);
        if (ret >= 0)
                clp->cl_cb_ident = ret;
        spin_unlock(&nn->nfs_client_lock);