[PATCH net-next v6 2/7] tun: Keep hdr_len in tun_get_user()

[Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>]

hdr_len is repeatedly used so keep it in a local variable.

Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
Reviewed-by: Willem de Bruijn <willemb@xxxxxxxxxx>
---
 drivers/net/tun.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 4b189cbd28e63ec6325073d9a7678f4210bff3e1..c204c1c0d75bc7d336ec315099a5a60d5d70ea82 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1747,6 +1747,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 	struct virtio_net_hdr gso = { 0 };
 	int good_linear;
 	int copylen;
+	int hdr_len = 0;
 	bool zerocopy = false;
 	int err;
 	u32 rxhash = 0;
@@ -1773,19 +1774,21 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		if (!copy_from_iter_full(&gso, sizeof(gso), from))
 			return -EFAULT;
 
-		if ((gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
-		    tun16_to_cpu(tun, gso.csum_start) + tun16_to_cpu(tun, gso.csum_offset) + 2 > tun16_to_cpu(tun, gso.hdr_len))
-			gso.hdr_len = cpu_to_tun16(tun, tun16_to_cpu(tun, gso.csum_start) + tun16_to_cpu(tun, gso.csum_offset) + 2);
+		hdr_len = tun16_to_cpu(tun, gso.hdr_len);
 
-		if (tun16_to_cpu(tun, gso.hdr_len) > len)
+		if (gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
+			hdr_len = max(tun16_to_cpu(tun, gso.csum_start) + tun16_to_cpu(tun, gso.csum_offset) + 2, hdr_len);
+			gso.hdr_len = cpu_to_tun16(tun, hdr_len);
+		}
+
+		if (hdr_len > len)
 			return -EINVAL;
 		iov_iter_advance(from, vnet_hdr_sz - sizeof(gso));
 	}
 
 	if ((tun->flags & TUN_TYPE_MASK) == IFF_TAP) {
 		align += NET_IP_ALIGN;
-		if (unlikely(len < ETH_HLEN ||
-			     (gso.hdr_len && tun16_to_cpu(tun, gso.hdr_len) < ETH_HLEN)))
+		if (unlikely(len < ETH_HLEN || (hdr_len && hdr_len < ETH_HLEN)))
 			return -EINVAL;
 	}
 
@@ -1798,9 +1801,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		 * enough room for skb expand head in case it is used.
 		 * The rest of the buffer is mapped from userspace.
 		 */
-		copylen = gso.hdr_len ? tun16_to_cpu(tun, gso.hdr_len) : GOODCOPY_LEN;
-		if (copylen > good_linear)
-			copylen = good_linear;
+		copylen = min(hdr_len ? hdr_len : GOODCOPY_LEN, good_linear);
 		linear = copylen;
 		iov_iter_advance(&i, copylen);
 		if (iov_iter_npages(&i, INT_MAX) <= MAX_SKB_FRAGS)
@@ -1821,10 +1822,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 	} else {
 		if (!zerocopy) {
 			copylen = len;
-			if (tun16_to_cpu(tun, gso.hdr_len) > good_linear)
-				linear = good_linear;
-			else
-				linear = tun16_to_cpu(tun, gso.hdr_len);
+			linear = min(hdr_len, good_linear);
 		}
 
 		if (frags) {

-- 
2.48.1