tfile->tun could be detached before we close the tun fd,
via tun_detach_all(), so it should not be used to check for
tfile->tx_array.

As Jason suggested, we probably have to clean it up
unconditionally, but this requires to check if it is initialized
or not. Currently skb_array_cleanup() doesn't have such a check,
so I check it in the caller, it is ugly but we can always
improve it in net-next.

Reported-by: Dmitry Vyukov <dvyu...@google.com>
Fixes: 1576d9860599 ("tun: switch to use skb array for tx")
Cc: Jason Wang <jasow...@redhat.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
 drivers/net/tun.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 4f4a842a1c9c..4c85474ffbaf 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -657,7 +657,7 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
                            tun->dev->reg_state == NETREG_REGISTERED)
                                unregister_netdevice(tun->dev);
                }
-               if (tun)
+               if (tfile->tx_array.ring.queue)
                        skb_array_cleanup(&tfile->tx_array);
                sock_put(&tfile->sk);
        }
@@ -2851,6 +2851,8 @@ static int tun_chr_open(struct inode *inode, struct file 
* file)
 
        sock_set_flag(&tfile->sk, SOCK_ZEROCOPY);
 
+       memset(&tfile->tx_array, 0, sizeof(tfile->tx_array));
+
        return 0;
 }
 
-- 
2.13.0

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