From: Yunjian Wang <redacted>

After setting callback for ubuf_info of skb, the callback
(vhost_net_zerocopy_callback) will be called to decrease
the refcount when freeing skb. But when an exception occurs
afterwards, the error handling in vhost handle_tx() will
try to decrease the same refcount again. This is wrong and
fix this by clearing ubuf_info when meeting errors.

Fixes: 4477138fa0ae ("tun: properly test for IFF_UP")
Fixes: 90e33d459407 ("tun: enable napi_gro_frags() for TUN/TAP driver")

Signed-off-by: Yunjian Wang <redacted>
---
  drivers/net/tun.c | 11 +++++++++++
  1 file changed, 11 insertions(+)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 2dc1988a8973..3614bb1b6d35 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c

@@ -1861,6 +1861,12 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
  	if (unlikely(!(tun->dev->flags & IFF_UP))) {
  		err = -EIO;
  		rcu_read_unlock();
+		if (zerocopy) {
+			skb_shinfo(skb)->destructor_arg = NULL;
+			skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
+			skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
+		}
+
  		goto drop;
  	}
  

@@ -1874,6 +1880,11 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
  
  		if (unlikely(headlen > skb_headlen(skb))) {
  			atomic_long_inc(&tun->dev->rx_dropped);
+			if (zerocopy) {
+				skb_shinfo(skb)->destructor_arg = NULL;
+				skb_shinfo(skb)->tx_flags &= ~SKBTX_DEV_ZEROCOPY;
+				skb_shinfo(skb)->tx_flags &= ~SKBTX_SHARED_FRAG;
+			}
  			napi_free_frags(&tfile->napi);
  			rcu_read_unlock();
  			mutex_unlock(&tfile->napi_mutex);