Subject: [PATCH 11/33] net: set default network namespace in init_dummy_netdev()

From: Josh Elsasser <[email-masked]>
Date: Sat, 26 Jan 2019 14:38:33 -0800

[ Upstream commit 35edfdc77f683c8fd27d7732af06cf6489af60a5 ]

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 <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/core/dev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 722d50dbf8a4..43f8a4fd4968 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8624,6 +8624,9 @@ 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.
-- 
2.20.1