[PATCH bpf] xdp: check device pointer before clearing

[Ilya Maximets]

We should not call 'ndo_bpf()' or 'dev_put()' with NULL argument.

Fixes: c9b47cc1fabc ("xsk: fix bug when trying to use both copy and zero-copy 
on one queue id")
Signed-off-by: Ilya Maximets <i.maxim...@samsung.com>
---

I'm not sure if this fixes any real NULL pointer dereference, but code
is not consistent anyway and should be fixed.

 net/xdp/xdp_umem.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index 2b18223e7eb8..9c6de4f114f8 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -143,6 +143,9 @@ static void xdp_umem_clear_dev(struct xdp_umem *umem)
        struct netdev_bpf bpf;
        int err;
 
+       if (!umem->dev)
+               return;
+
        if (umem->zc) {
                bpf.command = XDP_SETUP_XSK_UMEM;
                bpf.xsk.umem = NULL;
@@ -156,11 +159,9 @@ static void xdp_umem_clear_dev(struct xdp_umem *umem)
                        WARN(1, "failed to disable umem!\n");
        }
 
-       if (umem->dev) {
-               rtnl_lock();
-               xdp_clear_umem_at_qid(umem->dev, umem->queue_id);
-               rtnl_unlock();
-       }
+       rtnl_lock();
+       xdp_clear_umem_at_qid(umem->dev, umem->queue_id);
+       rtnl_unlock();
 
        if (umem->zc) {
                dev_put(umem->dev);
-- 
2.17.1