Re: [PATCH v1] hamradio: remove needs_free_netdev to avoid UAF

On Thu, 11 Nov 2021 22:14:02 +0800 Lin Ma wrote:

The former patch "defer 6pack kfree after unregister_netdev" reorders
the kfree of two buffer after the unregister_netdev to prevent the race
condition. It also adds free_netdev() function in sixpack_close(), which
is a direct copy from the similar code in mkiss_close().

However, in sixpack driver, the flag needs_free_netdev is set to true in
sp_setup(), hence the unregister_netdev() will free the netdev
automatically. Therefore, as the sp is netdev_priv, use-after-free
occurs.

This patch removes the needs_free_netdev = true and just let the
free_netdev to finish this deallocation task.

Signed-off-by: Lin Ma <redacted>

Fixes: 0b9111922b1f ("hamradio: defer 6pack kfree after unregister_netdev")