From: Subash Abhinov Kasiviswanathan <subashab@xxxxxxxxxxxxxx> commit 2abb5792387eb188b12051337d5dcd2cba615cb0 upstream. This allows the changelink operation to succeed if the mux_id was specified as an argument. Note that the mux_id must match the existing mux_id of the rmnet device or should be an unused mux_id. Fixes: 1dc49e9d164c ("net: rmnet: do not allow to change mux id if mux id is duplicated") Reported-and-tested-by: Alex Elder <elder@xxxxxxxxxx> Signed-off-by: Sean Tranchetti <stranche@xxxxxxxxxxxxxx> Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@xxxxxxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Cc: Guenter Roeck <linux@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c | 31 ++++++++++++--------- 1 file changed, 19 insertions(+), 12 deletions(-) --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c @@ -288,7 +288,6 @@ static int rmnet_changelink(struct net_d { struct rmnet_priv *priv = netdev_priv(dev); struct net_device *real_dev; - struct rmnet_endpoint *ep; struct rmnet_port *port; u16 mux_id; @@ -303,19 +302,27 @@ static int rmnet_changelink(struct net_d if (data[IFLA_RMNET_MUX_ID]) { mux_id = nla_get_u16(data[IFLA_RMNET_MUX_ID]); - if (rmnet_get_endpoint(port, mux_id)) { - NL_SET_ERR_MSG_MOD(extack, "MUX ID already exists"); - return -EINVAL; - } - ep = rmnet_get_endpoint(port, priv->mux_id); - if (!ep) - return -ENODEV; - hlist_del_init_rcu(&ep->hlnode); - hlist_add_head_rcu(&ep->hlnode, &port->muxed_ep[mux_id]); + if (mux_id != priv->mux_id) { + struct rmnet_endpoint *ep; + + ep = rmnet_get_endpoint(port, priv->mux_id); + if (!ep) + return -ENODEV; + + if (rmnet_get_endpoint(port, mux_id)) { + NL_SET_ERR_MSG_MOD(extack, + "MUX ID already exists"); + return -EINVAL; + } + + hlist_del_init_rcu(&ep->hlnode); + hlist_add_head_rcu(&ep->hlnode, + &port->muxed_ep[mux_id]); - ep->mux_id = mux_id; - priv->mux_id = mux_id; + ep->mux_id = mux_id; + priv->mux_id = mux_id; + } } if (data[IFLA_RMNET_FLAGS]) {