netdev - Re: [PATCH net] RDMA/core: fix UAF in ib_get_eth

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Date: Thu, 28 Mar 2024 12:24:37 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Denis Kirjanov <kirjanov@...il.com>
Cc: netdev@...r.kernel.org, jgg@...pe.ca, leon@...nel.org, 
	Denis Kirjanov <dkirjanov@...e.de>, syzbot+5fe14f2ff4ccbace9a26@...kaller.appspotmail.com
Subject: Re: [PATCH net] RDMA/core: fix UAF in ib_get_eth_speed

On Thu, Mar 28, 2024 at 12:23 PM Denis Kirjanov <kirjanov@...il.com> wrote:
>
> 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) {
>
> Reported-by: syzbot+5fe14f2ff4ccbace9a26@...kaller.appspotmail.com
> Fixes: d41861942fc55 ("IB/core: Add generic function to extract IB speed from netdev")
> Signed-off-by: Denis Kirjanov <dkirjanov@...e.de>
> ---
>  drivers/infiniband/core/verbs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
> index 94a7f3b0c71c..aa4f642e7de9 100644
> --- a/drivers/infiniband/core/verbs.c
> +++ b/drivers/infiniband/core/verbs.c
> @@ -1976,11 +1976,11 @@ 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);
>         if (!netdev)

This can not be right, we could return -ENODEV whild rtnl is kept locked.

>                 return -ENODEV;
>
> -       rtnl_lock();
>         rc = __ethtool_get_link_ksettings(netdev, &lksettings);
>         rtnl_unlock();
>
> --
> 2.30.2
>