Re: [PATCH v2 net] RDMA/core: fix UAF in ib_get_eth_speed

[Ratheesh Kannoth <rkannoth@marvell.com>]

On 2024-03-28 at 17:02:33, Denis Kirjanov (kirjanov@gmail.com) wrote:
> A call to ib_device_get_netdev from ib_get_eth_speed
> may lead to a race condition while accessing a netdevice
> instance since we don't hold the rtnl lock while checking
> the registration state:
> 	if (res && res->reg_state != NETREG_REGISTERED) {
>
> v2: unlock rtnl on error patch
>
> Reported-by: syzbot+5fe14f2ff4ccbace9a26@syzkaller.appspotmail.com
> Fixes: d41861942fc55 ("IB/core: Add generic function to extract IB speed from netdev")
> Signed-off-by: Denis Kirjanov <dkirjanov@suse.de>
> ---
>  drivers/infiniband/core/verbs.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
> index 94a7f3b0c71c..9c09d8c328b4 100644
> --- a/drivers/infiniband/core/verbs.c
> +++ b/drivers/infiniband/core/verbs.c
> @@ -1976,11 +1976,13 @@ int ib_get_eth_speed(struct ib_device *dev, u32 port_num, u16 *speed, u8 *width)
>  	if (rdma_port_get_link_layer(dev, port_num) != IB_LINK_LAYER_ETHERNET)
>  		return -EINVAL;
>
> +	rtnl_lock();
>  	netdev = ib_device_get_netdev(dev, port_num);
ib_device_get_netdev() hold ref to dev before checking reg_state, isn't it enough ?

> -	if (!netdev)
> +	if (!netdev) {
> +		rtnl_unlock()
>  		return -ENODEV;
> +	}
>
> -	rtnl_lock();
>  	rc = __ethtool_get_link_ksettings(netdev, &lksettings);
>  	rtnl_unlock();
>
> --
> 2.30.2
>