[Make-wifi-fast] [PATCH bpf-next] xdp: Fix race in dev_map_hash_update_elem() when replacing element

[Toke Høiland-Jørgensen]

Toke Høiland-Jørgensen <toke at redhat.com> writes:

> syzbot found a crash in dev_map_hash_update_elem(), when replacing an
> element with a new one. Jesper correctly identified the cause of the crash
> as a race condition between the initial lookup in the map (which is done
> before taking the lock), and the removal of the old element.
>
> Rather than just add a second lookup into the hashmap after taking the
> lock, fix this by reworking the function logic to take the lock before the
> initial lookup.
>
> Fixes: 6f9d451ab1a3 ("xdp: Add devmap_hash map type for looking up devices by hashed index")
> Reported-and-tested-by: syzbot+4e7a85b1432052e8d6f8 at syzkaller.appspotmail.com
> Signed-off-by: Toke Høiland-Jørgensen <toke at redhat.com>
> ---

Oops, this wasn't supposed to go to linux-wireless and make-wifi-fast;
apologies for the noise! :)

-Toke