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tun: Optimise handling of bogus gso->hdr_len 

As all current versions of virtio_net generate a value for the
header length that's too small, we should optimise this so that
we don't copy it twice.  This can be done by ensuring that it is
at least as large as the place where we'll write the checksum.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2009-06-08 00:20:01 -07:00 committed by David S. Miller
parent b82f08ea16
commit 4909122fb8
1 changed files with 4 additions and 0 deletions
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4
drivers/net/tun.c
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@ -565,6 +565,10 @@ static __inline__ ssize_t tun_get_user(struct tun_struct *tun,
if (memcpy_fromiovecend((void *)&gso, iv, offset, sizeof(gso)))
return -EFAULT;
if ((gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
gso.csum_start + gso.csum_offset + 2 > gso.hdr_len)
gso.hdr_len = gso.csum_start + gso.csum_offset + 2;
if (gso.hdr_len > len)
return -EINVAL;
offset += sizeof(pi);