Re: WARNING in hwsim_new_radio_nl

[Johannes Berg]

Hi syzbot keepers,

On Mon, 2020-04-13 at 07:05 -0700, syzbot wrote:
> syzbot has bisected this bug to:
> 
> commit 01cacb00b35cb62b139f07d5f84bcf0eeda8eff6
> Author: Paolo Abeni <pabeni@xxxxxxxxxx>
> Date:   Fri Mar 27 21:48:51 2020 +0000
> 
>     mptcp: add netlink-based PM
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10225bb3e00000

This is, fairly obviously, incorrect. Same with the bisection for
6693adf1698864d21734, which is really the same underlying problem as
this one (though at a different code site).

However, it stands out that this was bisected to a commit that adds a
new generic netlink family in both cases.

This makes sense - the reproducer identifies the family by *number*, but
that number isn't stable, generic netlink families should be identified
by *name*.

Perhaps somehow syzbot could be taught that, so that the bisection is
stable across kernels with different generic netlink families
registered?

Alternatively, we _could_ add some kind of stable ID mode, but I'm not
sure we really want to ... since that would mean people start hardcoding
IDs?

johannes