[PATCH net-next 1/1] driver: tun: Move tun check into the block of TUNSETIFF condition check

From: Gao Feng <redacted>

When cmd is TUNSETIFF and tun is not null, the original codes go ahead,
then reach the default case of switch(cmd) and set the ret is -EINVAL.
It is not clear for readers.

Now move the tun check into the block of TUNSETIFF condition check, and
return -EEXIST instead of -EINVAL when the tfile already owns one tun.

Signed-off-by: Gao Feng <redacted>
---
 drivers/net/tun.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9328568..9142db8 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c

@@ -2005,7 +2005,11 @@ static long __tun_chr_ioctl(struct file *file, unsigned int cmd,
 	rtnl_lock();
 
 	tun = __tun_get(tfile);
-	if (cmd == TUNSETIFF && !tun) {
+	if (cmd == TUNSETIFF) {
+		ret = -EEXIST;
+		if (tun)
+			goto unlock;
+
 		ifr.ifr_name[IFNAMSIZ-1] = '\0';
 
 		ret = tun_set_iff(sock_net(&tfile->sk), file, &ifr);

-- 
1.9.1