net: tun: rebuild error handling in tun_get_user

The error handling in tun_get_user is very scattered.
This patch unifies error handling, reduces duplication of code, and
makes the logic clearer.

Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index addef00..f5f412e 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1746,7 +1746,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
        u32 rxhash = 0;
        int skb_xdp = 1;
        bool frags = tun_napi_frags_enabled(tfile);
-       enum skb_drop_reason drop_reason;
+       enum skb_drop_reason drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
 
        if (!(tun->flags & IFF_NO_PI)) {
                if (len < sizeof(pi))
@@ -1807,10 +1807,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
                 * skb was created with generic XDP routine.
                 */
                skb = tun_build_skb(tun, tfile, from, &gso, len, &skb_xdp);
-               if (IS_ERR(skb)) {
-                       dev_core_stats_rx_dropped_inc(tun->dev);
-                       return PTR_ERR(skb);
-               }
+               err = PTR_ERR_OR_ZERO(skb);
+               if (err)
+                       goto drop;
                if (!skb)
                        return total_len;
        } else {
@@ -1835,13 +1834,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
                                            noblock);
                }
 
-               if (IS_ERR(skb)) {
-                       if (PTR_ERR(skb) != -EAGAIN)
-                               dev_core_stats_rx_dropped_inc(tun->dev);
-                       if (frags)
-                               mutex_unlock(&tfile->napi_mutex);
-                       return PTR_ERR(skb);
-               }
+               err = PTR_ERR_OR_ZERO(skb);
+               if (err)
+                       goto drop;
 
                if (zerocopy)
                        err = zerocopy_sg_from_iter(skb, from);
@@ -1851,27 +1846,14 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
                if (err) {
                        err = -EFAULT;
                        drop_reason = SKB_DROP_REASON_SKB_UCOPY_FAULT;
-drop:
-                       dev_core_stats_rx_dropped_inc(tun->dev);
-                       kfree_skb_reason(skb, drop_reason);
-                       if (frags) {
-                               tfile->napi.skb = NULL;
-                               mutex_unlock(&tfile->napi_mutex);
-                       }
-
-                       return err;
+                       goto drop;
                }
        }
 
        if (virtio_net_hdr_to_skb(skb, &gso, tun_is_little_endian(tun))) {
                atomic_long_inc(&tun->rx_frame_errors);
-               kfree_skb(skb);
-               if (frags) {
-                       tfile->napi.skb = NULL;
-                       mutex_unlock(&tfile->napi_mutex);
-               }
-
-               return -EINVAL;
+               err = -EINVAL;
+               goto free_skb;
        }
 
        switch (tun->flags & TUN_TYPE_MASK) {
@@ -1887,9 +1869,8 @@ drop:
                                pi.proto = htons(ETH_P_IPV6);
                                break;
                        default:
-                               dev_core_stats_rx_dropped_inc(tun->dev);
-                               kfree_skb(skb);
-                               return -EINVAL;
+                               err = -EINVAL;
+                               goto drop;
                        }
                }
 
@@ -1931,11 +1912,7 @@ drop:
                        if (ret != XDP_PASS) {
                                rcu_read_unlock();
                                local_bh_enable();
-                               if (frags) {
-                                       tfile->napi.skb = NULL;
-                                       mutex_unlock(&tfile->napi_mutex);
-                               }
-                               return total_len;
+                               goto unlock_frags;
                        }
                }
                rcu_read_unlock();
@@ -2015,6 +1992,22 @@ napi_busy:
                tun_flow_update(tun, rxhash, tfile);
 
        return total_len;
+
+drop:
+       if (err != -EAGAIN)
+               dev_core_stats_rx_dropped_inc(tun->dev);
+
+free_skb:
+       if (!IS_ERR_OR_NULL(skb))
+               kfree_skb_reason(skb, drop_reason);
+
+unlock_frags:
+       if (frags) {
+               tfile->napi.skb = NULL;
+               mutex_unlock(&tfile->napi_mutex);
+       }
+
+       return err ?: total_len;
 }
 
 static ssize_t tun_chr_write_iter(struct kiocb *iocb, struct iov_iter *from)