Re: [PATCH v1 net-next 4/6] socket: Remove kernel socket conversion except for net/rds/.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Chuck Lever <chuck.lever@oracle.com>
Date: Thu, 22 May 2025 12:38:03 -0400
> On 5/22/25 4:55 AM, Paolo Abeni wrote:
> > On 5/17/25 5:50 AM, Kuniyuki Iwashima wrote:
> >> Since commit 26abe14379f8 ("net: Modify sk_alloc to not reference
> >> count the netns of kernel sockets."), TCP kernel socket has caused
> >> many UAF.
> >>
> >> We have converted such sockets to hold netns refcnt, and we have
> >> the same pattern in cifs, mptcp, nvme, rds, smc, and sunrpc.
> >>
> >>   __sock_create_kern(..., &sock);
> >>   sk_net_refcnt_upgrade(sock->sk);
> >>
> >> Let's drop the conversion and use sock_create_kern() instead.
> >>
> >> The changes for cifs, mptcp, nvme, and smc are straightforward.
> >>
> >> For sunrpc, we call sock_create_net() for IPPROTO_TCP only and still
> >> call __sock_create_kern() for others.
> >>
> >> For rds, we cannot drop sk_net_refcnt_upgrade() for accept()ed
> >> sockets.
> >>
> >> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> > 
> > This LGTM, but is touching a few other subsystems, it would be great to
> > collect acks from the relevant maintainers: I'm adding a few CCs.
> > 
> > Direct link to the series:
> > 
> > https://lore.kernel.org/all/20250517035120.55560-1-kuniyu@amazon.com/#t
> 
> Thank you, Paolo, for forwarding this series.
> 
> For all hunks modifying net/sunrpc/svcsock.c and
> net/handshake/handshake-test.c:
> 
>   Acked-by: Chuck Lever <chuck.lever@oracle.com>
> 
> Regarding patch 4/6:
> 
> This paragraph in the patch description needs to explain /why/ sunrpc
> is an exception:
> 
> > For sunrpc, we call sock_create_net() for IPPROTO_TCP only and still
> > call __sock_create_kern() for others.

Sorry I noticed this sentence was not updated from the previous series.

I'll change it as follows

    For sunrpc, we call sk_net_refcnt_upgrade() for IPPROTO_TCP only
    so we use sock_create_kern() for TCP and keep __sock_create_kern()
    for others.


> 
> The below hunk doesn't seem related to the marquee purpose of this
> series. Should it be a separate patch with its own rationale?
> 
> @@ -1541,8 +1544,8 @@ static struct svc_xprt *svc_create_socket(struct
> svc_serv *serv,
>  	newlen = error;
> 
>  	if (protocol == IPPROTO_TCP) {
> -		sk_net_refcnt_upgrade(sock->sk);

The part above is related, and the below is not, using the old
style warned by checkpatch, so I cleaned it up while at it but
didn't think it's worth a patch.  I'm fine to drop it.


> -		if ((error = kernel_listen(sock, 64)) < 0)
> +		error = kernel_listen(sock, 64);
> +		if (error < 0)
>  			goto bummer;
>  	}
>