Subject: Re: [PATCH bpf-next] xdp: Fix race in dev_map_hash_update_elem() when replacing element

From: Jesper Dangaard Brouer <[email-masked]>
Date: Sun, 8 Sep 2019 13:28:22 +0200

On Sun,  8 Sep 2019 09:20:16 +0100
Toke Høiland-Jørgensen <[email-masked]> wrote:

> 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: [email-masked]
> Signed-off-by: Toke Høiland-Jørgensen <[email-masked]>

Acked-by: Jesper Dangaard Brouer <[email-masked]>

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer