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

[Chuck Lever]

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 at 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 at 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.

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


>> diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
>> index 37a2ba38f10e..c7b4f5a7cca1 100644
>> --- a/fs/smb/client/connect.c
>> +++ b/fs/smb/client/connect.c
>> @@ -3348,21 +3348,14 @@ generic_ip_connect(struct TCP_Server_Info *server)
>>  		socket = server->ssocket;
>>  	} else {
>>  		struct net *net = cifs_net_ns(server);
>> -		struct sock *sk;
>>  
>> -		rc = __sock_create_kern(net, sfamily, SOCK_STREAM,
>> -					IPPROTO_TCP, &server->ssocket);
>> +		rc = sock_create_kern(net, sfamily, SOCK_STREAM,
>> +				      IPPROTO_TCP, &server->ssocket);
>>  		if (rc < 0) {
>>  			cifs_server_dbg(VFS, "Error %d creating socket\n", rc);
>>  			return rc;
>>  		}
>>  
>> -		sk = server->ssocket->sk;
>> -		__netns_tracker_free(net, &sk->ns_tracker, false);
>> -		sk->sk_net_refcnt = 1;
>> -		get_net_track(net, &sk->ns_tracker, GFP_KERNEL);
>> -		sock_inuse_add(net, 1);
> 
> AFAICS the above implicitly adds a missing net_passive_dec(net), which
> in turns looks like a separate bugfix. What about adding a separate
> patch introducing that line? Could be in the same series to simplify the
> processing.
> 
> Thanks,
> 
> Paolo
> 


-- 
Chuck Lever