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    Subject[ 017/171 ] vhost/net: fix heads usage of ubuf_info
    3.6.11.2 stable review patch.
    If anyone has any objections, please let me know.

    ------------------

    From: "Michael S. Tsirkin" <mst@redhat.com>

    [ Upstream commit 46aa92d1ba162b4b3d6b7102440e459d4e4ee255 ]

    ubuf info allocator uses guest controlled head as an index,
    so a malicious guest could put the same head entry in the ring twice,
    and we will get two callbacks on the same value.
    To fix use upend_idx which is guaranteed to be unique.

    Reported-by: Rusty Russell <rusty@rustcorp.com.au>
    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
    Cc: stable@kernel.org
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    ---
    drivers/vhost/net.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
    index 7f93f34..156a360 100644
    --- a/drivers/vhost/net.c
    +++ b/drivers/vhost/net.c
    @@ -235,7 +235,8 @@ static void handle_tx(struct vhost_net *net)
    msg.msg_controllen = 0;
    ubufs = NULL;
    } else {
    - struct ubuf_info *ubuf = &vq->ubuf_info[head];
    + struct ubuf_info *ubuf;
    + ubuf = vq->ubuf_info + vq->upend_idx;

    vq->heads[vq->upend_idx].len = len;
    ubuf->callback = vhost_zerocopy_callback;
    --
    1.7.10.4



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