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    Subject[PATCH V2 2/3] tuntap: forbid calling TUNSETIFF when detached
    Date
    Michael points out that even after Stefan's fix the TUNSETIFF is still allowed
    to create a new tap device. This because we only check tfile->tun but the
    tfile->detached were introduced. Fix this by failing early in tun_set_iff() if
    the file is detached. After this fix, there's no need to do the check again in
    tun_set_iff(), so this patch removes it.

    Cc: Michael S. Tsirkin <mst@redhat.com>
    Cc: Stefan Hajnoczi <stefanha@redhat.com>
    Signed-off-by: Jason Wang <jasowang@redhat.com>
    ---
    drivers/net/tun.c | 5 +++--
    1 files changed, 3 insertions(+), 2 deletions(-)

    diff --git a/drivers/net/tun.c b/drivers/net/tun.c
    index aa963c4..a36b56f 100644
    --- a/drivers/net/tun.c
    +++ b/drivers/net/tun.c
    @@ -488,8 +488,6 @@ static int tun_attach(struct tun_struct *tun, struct file *file)
    err = -EINVAL;
    if (rtnl_dereference(tfile->tun))
    goto out;
    - if (tfile->detached && tun != tfile->detached)
    - goto out;

    err = -EBUSY;
    if (!(tun->flags & TUN_TAP_MQ) && tun->numqueues == 1)
    @@ -1543,6 +1541,9 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
    struct net_device *dev;
    int err;

    + if (tfile->detached)
    + return -EINVAL;
    +
    dev = __dev_get_by_name(net, ifr->ifr_name);
    if (dev) {
    if (ifr->ifr_flags & IFF_TUN_EXCL)
    --
    1.7.1


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