Merge: vrf: Drop existing dst reference in vrf_ip6_input_dst

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/7507

This is the P2 backport for VRF.

JIRA: https://issues.redhat.com/browse/RHEL-115636
Upstream Status: linux.git

commit f388f80
Author: Stanislav Fomichev <sdf@fomichev.me>
Date:   Fri Jul 25 09:00:43 2025 -0700

    vrf: Drop existing dst reference in vrf_ip6_input_dst

    Commit ff3fbcd ("selftests: tc: Add generic erspan_opts matching support
    for tc-flower") started triggering the following kmemleak warning:

    unreferenced object 0xffff888015fb0e00 (size 512):
      comm "softirq", pid 0, jiffies 4294679065
      hex dump (first 32 bytes):
        00 00 00 00 00 00 00 00 40 d2 85 9e ff ff ff ff  ........@.......
        41 69 59 9d ff ff ff ff 00 00 00 00 00 00 00 00  AiY.............
      backtrace (crc 30b71e8b):
        __kmalloc_noprof+0x359/0x460
        metadata_dst_alloc+0x28/0x490
        erspan_rcv+0x4f1/0x1160 [ip_gre]
        gre_rcv+0x217/0x240 [ip_gre]
        gre_rcv+0x1b8/0x400 [gre]
        ip_protocol_deliver_rcu+0x31d/0x3a0
        ip_local_deliver_finish+0x37d/0x620
        ip_local_deliver+0x174/0x460
        ip_rcv+0x52b/0x6b0
        __netif_receive_skb_one_core+0x149/0x1a0
        process_backlog+0x3c8/0x1390
        __napi_poll.constprop.0+0xa1/0x390
        net_rx_action+0x59b/0xe00
        handle_softirqs+0x22b/0x630
        do_softirq+0xb1/0xf0
        __local_bh_enable_ip+0x115/0x150

    vrf_ip6_input_dst unconditionally sets skb dst entry, add a call to
    skb_dst_drop to drop any existing entry.

    Cc: David Ahern <dsahern@kernel.org>
    Reviewed-by: Ido Schimmel <idosch@nvidia.com>
    Fixes: 9ff7438 ("net: vrf: Handle ipv6 multicast and link-local addresses")
    Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
    Link: https://patch.msgid.link/20250725160043.350725-1-sdf@fomichev.me
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Antoine Tenart <atenart@redhat.com>

Approved-by: Paolo Abeni <pabeni@redhat.com>
Approved-by: Hangbin Liu <haliu@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

drivers/net/vrf.c

@@ -1345,6 +1345,8 @@ static void vrf_ip6_input_dst(struct sk_buff *skb, struct net_device *vrf_dev,
 	struct net *net = dev_net(vrf_dev);
 	struct rt6_info *rt6;
 
+	skb_dst_drop(skb);
+
 	rt6 = vrf_ip6_route_lookup(net, vrf_dev, &fl6, ifindex, skb,
 				   RT6_LOOKUP_F_HAS_SADDR | RT6_LOOKUP_F_IFACE);
 	if (unlikely(!rt6))