On Tue, Jun 06, 2023 at 08:24:54AM +0200, Mirsad Goran Todorovac wrote:

quoted

On 5/31/23 20:11, Guillaume Nault wrote:

quoted

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);