NACK/Cmnt: [SRU v2][F/gke][PATCH] net/packet: rx_owner_map depends on pg_vec

[Stefan Bader]

On 27.01.22 09:00, Khalid Elmously wrote:
> From: Willem de Bruijn <willemb at google.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1959173
> 
> Packet sockets may switch ring versions. Avoid misinterpreting state
> between versions, whose fields share a union. rx_owner_map is only
> allocated with a packet ring (pg_vec) and both are swapped together.
> If pg_vec is NULL, meaning no packet ring was allocated, then neither
> was rx_owner_map. And the field may be old state from a tpacket_v3.
> 
> Fixes: 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race condition")
> Reported-by: Syzbot <syzbot+1ac0994a0a0c55151121 at syzkaller.appspotmail.com>
> Signed-off-by: Willem de Bruijn <willemb at google.com>
> Reviewed-by: Eric Dumazet <edumazet at google.com>
> Link: https://lore.kernel.org/r/20211215143937.106178-1-willemdebruijn.kernel@gmail.com
> Signed-off-by: Jakub Kicinski <kuba at kernel.org>
> (cherry picked from commit ec6af094ea28f0f2dda1a6a33b14cd57e36a9755)
> Signed-off-by: Khalid Elmously <khalid.elmously at canonical.com>
> ---

Not sure this was ever picked up for any GKE kernel but it was applied to 
focal:linux via stable and is part of Ubuntu-5.4.0-100.113 in the current 
2022.01.31 cycle. This got picked up by Ubuntu-gke-5.4.0-1063.66 so it does not 
need to be done again. Thanks.

-Stefan

>   net/packet/af_packet.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 46943a18a10d..76c2dca7f0a5 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -4492,9 +4492,10 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
>   	}
>   
>   out_free_pg_vec:
> -	bitmap_free(rx_owner_map);
> -	if (pg_vec)
> +	if (pg_vec) {
> +		bitmap_free(rx_owner_map);
>   		free_pg_vec(pg_vec, order, req->tp_block_nr);
> +	}
>   out:
>   	return err;
>   }

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