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    Subject[PATCH 3.10 222/250] tun: Fix TUN_PKT_STRIP setting
    Date
    From: Herbert Xu <herbert@gondor.apana.org.au>

    commit 2eb783c43e7cf807a45899c10ed556b6dc116625 upstream.

    We set the flag TUN_PKT_STRIP if the user buffer provided is too
    small to contain the entire packet plus meta-data. However, this
    has been broken ever since we added GSO meta-data. VLAN acceleration
    also has the same problem.

    This patch fixes this by taking both into account when setting the
    TUN_PKT_STRIP flag.

    The fact that this has been broken for six years without anyone
    realising means that nobody actually uses this flag.

    Fixes: f43798c27684 ("tun: Allow GSO using virtio_net_hdr")
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    [wt: no tuntap VLAN offloading in 3.10]
    Signed-off-by: Willy Tarreau <w@1wt.eu>
    ---
    drivers/net/tun.c | 12 ++++++++----
    1 file changed, 8 insertions(+), 4 deletions(-)

    diff --git a/drivers/net/tun.c b/drivers/net/tun.c
    index 5824971..ea6ada3 100644
    --- a/drivers/net/tun.c
    +++ b/drivers/net/tun.c
    @@ -1272,12 +1272,16 @@ static ssize_t tun_put_user(struct tun_struct *tun,
    {
    struct tun_pi pi = { 0, skb->protocol };
    ssize_t total = 0;
    + int vnet_hdr_sz = 0;
    +
    + if (tun->flags & TUN_VNET_HDR)
    + vnet_hdr_sz = tun->vnet_hdr_sz;

    if (!(tun->flags & TUN_NO_PI)) {
    if ((len -= sizeof(pi)) < 0)
    return -EINVAL;

    - if (len < skb->len) {
    + if (len < skb->len + vnet_hdr_sz) {
    /* Packet will be striped */
    pi.flags |= TUN_PKT_STRIP;
    }
    @@ -1287,9 +1291,9 @@ static ssize_t tun_put_user(struct tun_struct *tun,
    total += sizeof(pi);
    }

    - if (tun->flags & TUN_VNET_HDR) {
    + if (vnet_hdr_sz) {
    struct virtio_net_hdr gso = { 0 }; /* no info leak */
    - if ((len -= tun->vnet_hdr_sz) < 0)
    + if ((len -= vnet_hdr_sz) < 0)
    return -EINVAL;

    if (skb_is_gso(skb)) {
    @@ -1332,7 +1336,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
    if (unlikely(memcpy_toiovecend(iv, (void *)&gso, total,
    sizeof(gso))))
    return -EFAULT;
    - total += tun->vnet_hdr_sz;
    + total += vnet_hdr_sz;
    }

    len = min_t(int, skb->len, len);
    --
    2.8.0.rc2.1.gbe9624a
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