linux-kernel - Re: [ovs-dev] [PATCH net-next] net: openvswitch: allow providing upcall pid for the 'execute' command

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Message-ID: <20250703080411.21c45920@uranium>
Date: Thu, 3 Jul 2025 08:04:11 -0300
From: Flavio Leitner <fbl@...close.org>
To: Ilya Maximets <i.maximets@....org>
Cc: netdev@...r.kernel.org, dev@...nvswitch.org,
 linux-kernel@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>, Simon
 Horman <horms@...nel.org>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
 <pabeni@...hat.com>, "David S. Miller" <davem@...emloft.net>
Subject: Re: [ovs-dev] [PATCH net-next] net: openvswitch: allow providing
 upcall pid for the 'execute' command

On Thu, 3 Jul 2025 10:38:49 +0200
Ilya Maximets <i.maximets@....org> wrote:

> On 7/3/25 1:08 AM, Flavio Leitner wrote:
> >>>> @@ -651,6 +654,10 @@ static int ovs_packet_cmd_execute(struct sk_buff
> >>>> *skb, struct genl_info *info) !!(hash & OVS_PACKET_HASH_L4_BIT));
> >>>>  	}
> >>>>  
> >>>> +	if (a[OVS_PACKET_ATTR_UPCALL_PID])
> >>>> +		upcall_pid =
> >>>> nla_get_u32(a[OVS_PACKET_ATTR_UPCALL_PID]);
> >>>> +	OVS_CB(packet)->upcall_pid = upcall_pid;  
> > 
> > Since this is coming from userspace, does it make sense to check if the
> > upcall_pid is one of the pids in the dp->upcall_portids array?  
> 
> Not really.  IMO, this would be an unnecessary artificial restriction.
> We're not concerned about security here since OVS_PACKET_CMD_EXECUTE
> requires the same privileges as the OVS_DP_CMD_NEW or the
> OVS_DP_CMD_SET.

What if the userspace is buggy or compromised?
It seems netlink API will return -ECONNREFUSED and the upcall is dropped.
Therefore, we would be okay either way, correct?