Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> writes:
> On Fri, Jan 7, 2022 at 10:31 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote:
>>
>> The bpf_xdp_link_update() function didn't check the program type before
>> updating the program, which made it possible to install any program type as
>> an XDP program, which is obviously not good. Syzbot managed to trigger this
>> by swapping in an LWT program on the XDP hook which would crash in a helper
>> call.
>>
>> Fix this by adding a check and bailing out if the types don't match.
>>
>> Fixes: 026a4c28e1db ("bpf, xdp: Implement LINK_UPDATE for BPF XDP link")
>> Reported-by: syzbot+983941aa85af6ded1fd9@xxxxxxxxxxxxxxxxxxxxxxxxx
>> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
>> ---
>
> The fix looks good to me, thanks. I'd love it if this was done
> generically in link_update, but each link type has its own locking
> schema for link->prog, so I didn't figure out a way to do this in a
> centralized way.
Yeah, moving it to be a generic check was my first thought as well, but
I came to the same conclusion :)
> Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Thanks!
-Toke
