Re: [syzbot] WARNING in __static_key_slow_dec

From: Jussi Maki
Date: Sun Sep 05 2021 - 06:08:21 EST

On Sat, Sep 4, 2021 at 6:20 AM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
> Looks like a jump label usage bug ("jump label: negative count!") may
> have been introduced, presumably with the following commit:
> 9e2ee5c7e7c3 ("net, bonding: Add XDP support to the bonding driver")
> Jussi, any idea?

Hey, thanks for looping me in.

The code in bond_xdp_set is unsafely assuming that it won't get called
multiple times with prog=NULL and that's likely the issue here. The
assumption seems to mostly hold as I haven't been able to reproduce
this locally yet, even with nested bonding or with non-XDP slaves in
the mix. I'll look into this more next week and try to decipher what
steps syzbot is doing. As soon as I have a repro + fix I'll send it to
the net tree.