netdev - Re: POSSIBLE BUG: selftests/net/fcnal-test.sh: [FAIL][FIX TESTED] in vrf "bind

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Date: Tue, 6 Jun 2023 20:07:36 +0200
From: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
To: Guillaume Nault <gnault@...hat.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: POSSIBLE BUG: selftests/net/fcnal-test.sh: [FAIL][FIX TESTED] in
 vrf "bind - ns-B IPv6 LLA" test

On 6/6/23 15:46, Guillaume Nault wrote:
> On Tue, Jun 06, 2023 at 08:24:54AM +0200, Mirsad Goran Todorovac wrote:
>> On 5/31/23 20:11, Guillaume Nault wrote:
>>> I believe this condition should be relaxed to allow the case where
>>> ->sk_bound_dev_if is oif's master device (and maybe there are other
>>> VRF cases to also consider).
>>
>> I've tried something like this, but something makes the kernel stuck
>> here:
>>
>> TEST: ping out, blocked by route - ns-B loopback IPv6                         [ OK ]
>> TEST: ping out, device bind, blocked by route - ns-B loopback IPv6            [ OK ]
>> TEST: ping in, blocked by route - ns-A loopback IPv6                          [ OK ]
>> TEST: ping out, unreachable route - ns-B loopback IPv6                        [ OK ]
>> TEST: ping out, device bind, unreachable route - ns-B loopback IPv6           [ OK ]
>>
>> #################################################################
>> With VRF
>>
>> [hanged process and kernel won't shutdown]
>>
>> The code is:
>>
>> ---
>>   net/ipv6/ping.c | 12 +++++++++++-
>>   1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
>> index c4835dbdfcff..81293e902293 100644
>> --- a/net/ipv6/ping.c
>> +++ b/net/ipv6/ping.c
>> @@ -73,6 +73,9 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
>>          struct rt6_info *rt;
>>          struct pingfakehdr pfh;
>>          struct ipcm6_cookie ipc6;
>> +       struct net *net = sock_net(sk);
>> +       struct net_device *dev = NULL;
>> +       struct net_device *mdev = NULL;
>>          err = ping_common_sendmsg(AF_INET6, msg, len, &user_icmph,
>>                                    sizeof(user_icmph));
>> @@ -111,10 +114,17 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
>>          else if (!oif)
>>                  oif = np->ucast_oif;
>> +       if (oif) {
>> +               dev = dev_get_by_index(net, oif);
>> +               mdev = netdev_master_upper_dev_get(dev);
>> +       }
>> +
>>          addr_type = ipv6_addr_type(daddr);
>>          if ((__ipv6_addr_needs_scope_id(addr_type) && !oif) ||
>>              (addr_type & IPV6_ADDR_MAPPED) ||
>> -           (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if))
>> +           (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if &&
>> +                   !(mdev && sk->sk_bound_dev_if &&
>> +                             mdev != dev_get_by_index(net, sk->sk_bound_dev_if))))
>>                  return -EINVAL;
>>          ipcm6_init_sk(&ipc6, np);
>>
>> I am obviously doing something very stupid.
> 
> The problem is that dev_get_by_index() holds a reference on 'dev' which
> your code never releases. Also netdev_master_upper_dev_get() needs rtnl
> protection. These should have generated some kernel oops.
> 
> You can try this instead:
> 
> -------- >8 --------
> 
> diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
> index c4835dbdfcff..f804c11e2146 100644
> --- a/net/ipv6/ping.c
> +++ b/net/ipv6/ping.c
> @@ -114,7 +114,8 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
>   	addr_type = ipv6_addr_type(daddr);
>   	if ((__ipv6_addr_needs_scope_id(addr_type) && !oif) ||
>   	    (addr_type & IPV6_ADDR_MAPPED) ||
> -	    (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if))
> +	    (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if &&
> +	     l3mdev_master_ifindex_by_index(sock_net(sk), oif) != sk->sk_bound_dev_if))
>   		return -EINVAL;
>   
>   	ipcm6_init_sk(&ipc6, np);

The problem appears to be fixed:

# ./fcnal-test.sh
[...]
TEST: ping out, vrf device+address bind - ns-B loopback IPv6                  [ OK ]
TEST: ping out, vrf device+address bind - ns-B IPv6 LLA                       [ OK ]
TEST: ping in - ns-A IPv6                                                     [ OK ]
[...]
Tests passed: 888
Tests failed:   0
#

The test passed in both environments that manifested the bug.

Tested-by: Mirsad Todorovac <mirsad.todorovac@....unizg.hr>

However, test on my AMD Ubuntu 22.04 box with 6.4-rc5 commit a4d7d7011219
has shown additional four failed tests:

root@...t # grep -n FAIL ../fcnal-test-4.log
90:TEST: ping local, VRF bind - VRF IP                                           [FAIL]
92:TEST: ping local, device bind - ns-A IP                                       [FAIL]
116:TEST: ping local, VRF bind - VRF IP                                           [FAIL]
118:TEST: ping local, device bind - ns-A IP                                       [FAIL]
root@...t #

But you would probably want me to file a separate bug report?

Best regards,
Mirsad