tun: Keep hdr_len in tun_get_user()

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

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250207-tun-v6-2-fb49cf8b103e@daynix.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 8a9a29031bd88916271342487e786649c467a23c..ecc32421dbb51fc3a79bddefa7ec79e2c81a161f 100644 (file)
--- 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) {