From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
DaeLyong Jeong <threeearcat@gmail.com>,
Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
Network Development <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Byoungyoung Lee <byoungyoung@purdue.edu>,
Kyungtae Kim <kt0755@gmail.com>,
bammanag@purdue.edu, Willem de Bruijn <willemb@google.com>
Subject: Re: WARNING in ip_recv_error
Date: Fri, 18 May 2018 14:59:18 -0400 [thread overview]
Message-ID: <CAF=yD-+Ai35L2=dGZzpjYYavBmBGNFXd-q9ju93WrPuewnhELg@mail.gmail.com> (raw)
In-Reply-To: <CAF=yD-+QLz63Z6h5OpC-ar+nHvpCpkVi79h9Vtn=7fzmHCK8Lg@mail.gmail.com>
On Fri, May 18, 2018 at 2:46 PM, Willem de Bruijn
<willemdebruijn.kernel@gmail.com> wrote:
> On Fri, May 18, 2018 at 2:44 PM, Willem de Bruijn
> <willemdebruijn.kernel@gmail.com> wrote:
>> On Fri, May 18, 2018 at 1:09 PM, Willem de Bruijn
>> <willemdebruijn.kernel@gmail.com> wrote:
>>> On Fri, May 18, 2018 at 11:44 AM, David Miller <davem@davemloft.net> wrote:
>>>> From: Eric Dumazet <eric.dumazet@gmail.com>
>>>> Date: Fri, 18 May 2018 08:30:43 -0700
>>>>
>>>>> We probably need to revert Willem patch (7ce875e5ecb8562fd44040f69bda96c999e38bbc)
>>>>
>>>> Is it really valid to reach ip_recv_err with an ipv6 socket?
>>>
>>> I guess the issue is that setsockopt IPV6_ADDRFORM is not an
>>> atomic operation, so that the socket is neither fully ipv4 nor fully
>>> ipv6 by the time it reaches ip_recv_error.
>>>
>>> sk->sk_socket->ops = &inet_dgram_ops;
>>> < HERE >
>>> sk->sk_family = PF_INET;
>>>
>>> Even calling inet_recv_error to demux would not necessarily help.
>>>
>>> Safest would be to look up by skb->protocol, similar to what
>>> ipv6_recv_error does to handle v4-mapped-v6.
>>>
>>> Or to make that function safe with PF_INET and swap the order
>>> of the above two operations.
>>>
>>> All sound needlessly complicated for this rare socket option, but
>>> I don't have a better idea yet. Dropping on the floor is not nice,
>>> either.
>>
>> Ensuring that ip_recv_error correctly handles packets from either
>> socket and removing the warning should indeed be good.
>>
>> It is robust against v4-mapped packets from an AF_INET6 socket,
>> but see caveat on reconnect below.
>>
>> The code between ipv6_recv_error for v4-mapped addresses and
>> ip_recv_error is essentially the same, the main difference being
>> whether to return network headers as sockaddr_in with SOL_IP
>> or sockaddr_in6 with SOL_IPV6.
>>
>> There are very few other locations in the stack that explicitly test
>> sk_family in this way and thus would be vulnerable to races with
>> IPV6_ADDRFORM.
>>
>> I'm not sure whether it is possible for a udpv6 socket to queue a
>> real ipv6 packet on the error queue, disconnect, connect to an
>> ipv4 address, call IPV6_ADDRFORM and then call ip_recv_error
>> on a true ipv6 packet. That would return buggy data, e.g., in
>> msg_name.
>
> In do_ipv6_setsockopt IPV6_ADDRFORM we can test that the
> error queue is empty, and then take its lock for the duration of the
> operation.
Actually, no reason to hold the lock. This setsockopt holds the socket
lock, which connect would need, too. So testing that the queue
is empty after testing that it is connected to a v4 address is
sufficient to ensure that no ipv6 packets are queued for reception.
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 4d780c7f0130..a975d6311341 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -199,6 +199,11 @@ static int do_ipv6_setsockopt(struct sock *sk,
int level, int optname,
if (ipv6_only_sock(sk) ||
!ipv6_addr_v4mapped(&sk->sk_v6_daddr)) {
retv = -EADDRNOTAVAIL;
break;
}
+ if (!skb_queue_empty(&sk->sk_error_queue)) {
+ retv = -EBUSY;
+ break;
+ }
+
fl6_free_socklist(sk);
__ipv6_sock_mc_close(sk);
After this it should be safe to remove the warning in ip_recv_error.
next prev parent reply other threads:[~2018-05-18 19:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-18 12:08 WARNING in ip_recv_error DaeRyong Jeong
2018-05-18 15:30 ` Eric Dumazet
2018-05-18 15:44 ` David Miller
2018-05-18 17:09 ` Willem de Bruijn
2018-05-18 18:44 ` Willem de Bruijn
2018-05-18 18:46 ` Willem de Bruijn
2018-05-18 18:59 ` Willem de Bruijn [this message]
2018-05-20 23:13 ` Willem de Bruijn
2018-05-23 15:40 ` Willem de Bruijn
2018-05-23 18:30 ` Willem de Bruijn
2018-05-24 8:00 ` Paolo Abeni
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