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net: tun: rebuild error handling in tun_get_user
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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>
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nashuiliang authored and davem330 committed Nov 14, 2022
1 parent b548b17 commit ab00af8
Showing 1 changed file with 29 additions and 36 deletions.
65 changes: 29 additions & 36 deletions drivers/net/tun.c
Original file line number Diff line number Diff line change
Expand Up @@ -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))
Expand Down Expand Up @@ -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 {
Expand All @@ -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);
Expand All @@ -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) {
Expand All @@ -1887,9 +1869,8 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
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;
}
}

Expand Down Expand Up @@ -1931,11 +1912,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
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();
Expand Down Expand Up @@ -2015,6 +1992,22 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
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)
Expand Down

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