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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Josh Elsasser <jelsasser@appneta.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.14 08/46] net: set default network namespace in init_dummy_netdev()
Date:   Mon,  4 Feb 2019 11:36:39 +0100
Message-Id: <20190204103610.172177409@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Josh Elsasser <jelsasser@appneta.com>

[ 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 <jelsasser@appneta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/core/dev.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7748,6 +7748,9 @@ int init_dummy_netdev(struct net_device
 	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.