net: set default network namespace in init_dummy_netdev()

Assign a default net namespace to netdevs created by init_dummy_netdev().
Fixes a NULL pointer dereference caused by busy-polling a socket bound to
an iwlwifi wireless device, which bumps the per-net BUSYPOLLRXPACKETS stat
if napi_poll() received packets:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000190
  IP: napi_busy_loop+0xd6/0x200
  Call Trace:
    sock_poll+0x5e/0x80
    do_sys_poll+0x324/0x5a0
    SyS_poll+0x6c/0xf0
    do_syscall_64+0x6b/0x1f0
    entry_SYSCALL_64_after_hwframe+0x3d/0xa2

Fixes: 7db6b048da3b ("net: Commonize busy polling code to focus on napi_id instead of socket")
Signed-off-by: Josh Elsasser <jelsasser@appneta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index 82f20022259da123e085e0e296e9cd1b97580999..8e276e0192a11add47992a6cca955e8eb13e66d8 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8712,6 +8712,9 @@ int init_dummy_netdev(struct net_device *dev)
        set_bit(__LINK_STATE_PRESENT, &dev->state);
        set_bit(__LINK_STATE_START, &dev->state);
 
+       /* napi_busy_loop stats accounting wants this */
+       dev_net_set(dev, &init_net);
+
        /* Note : We dont allocate pcpu_refcnt for dummy devices,
         * because users of this 'device' dont need to change
         * its refcount.