Re: [RFC PATCH 3/7] tun: allow use of BPF_PROG_TYPE_SCHED_CLS program type

[Alexei Starovoitov]

On Tue, Jan 05, 2021 at 02:24:12PM +0200, Yuri Benditovich wrote:
> This program type can set skb hash value. It will be useful
> when the tun will support hash reporting feature if virtio-net.
> 
> Signed-off-by: Yuri Benditovich <yuri.benditovich@xxxxxxxxxx>
> ---
>  drivers/net/tun.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 7959b5c2d11f..455f7afc1f36 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2981,6 +2981,8 @@ static int tun_set_ebpf(struct tun_struct *tun, struct tun_prog __rcu **prog_p,
>  		prog = NULL;
>  	} else {
>  		prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SOCKET_FILTER);
> +		if (IS_ERR(prog))
> +			prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SCHED_CLS);

Patches 1 and 2 are missing for me, so I couldn't review properly,
but this diff looks odd.
It allows sched_cls prog type to attach to tun.
That means everything that sched_cls progs can do will be done from tun hook?
sched_cls assumes l2 and can modify the packet.
I think crashes are inevitable.