Merge: net: decrease cached dst counters in dst_release

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6720

JIRA: https://issues.redhat.com/browse/RHEL-83031
Upstream Status: linux.git

commit 3a0a3ff
Author: Antoine Tenart <atenart@kernel.org>
Date:   Wed Mar 26 18:36:32 2025 +0100

    net: decrease cached dst counters in dst_release

    Upstream fix ac888d5 ("net: do not delay dst_entries_add() in
    dst_release()") moved decrementing the dst count from dst_destroy to
    dst_release to avoid accessing already freed data in case of netns
    dismantle. However in case CONFIG_DST_CACHE is enabled and OvS+tunnels
    are used, this fix is incomplete as the same issue will be seen for
    cached dsts:

      Unable to handle kernel paging request at virtual address ffff5aabf6b5c000
      Call trace:
       percpu_counter_add_batch+0x3c/0x160 (P)
       dst_release+0xec/0x108
       dst_cache_destroy+0x68/0xd8
       dst_destroy+0x13c/0x168
       dst_destroy_rcu+0x1c/0xb0
       rcu_do_batch+0x18c/0x7d0
       rcu_core+0x174/0x378
       rcu_core_si+0x18/0x30

    Fix this by invalidating the cache, and thus decrementing cached dst
    counters, in dst_release too.

    Fixes: d71785f ("net: add dst_cache to ovs vxlan lwtunnel")
    Signed-off-by: Antoine Tenart <atenart@kernel.org>
    Link: https://patch.msgid.link/20250326173634.31096-1-atenart@kernel.org
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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

Approved-by: Hangbin Liu <haliu@redhat.com>
Approved-by: Xin Long <lxin@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Augusto Caringi <acaringi@redhat.com>

Author: caringi

net/core/dst.c

@@ -167,6 +167,14 @@ static void dst_count_dec(struct dst_entry *dst)
 void dst_release(struct dst_entry *dst)
 {
 	if (dst && rcuref_put(&dst->__rcuref)) {
+#ifdef CONFIG_DST_CACHE
+		if (dst->flags & DST_METADATA) {
+			struct metadata_dst *md_dst = (struct metadata_dst *)dst;
+
+			if (md_dst->type == METADATA_IP_TUNNEL)
+				dst_cache_reset_now(&md_dst->u.tun_info.dst_cache);
+		}
+#endif
 		dst_count_dec(dst);
 		call_rcu_hurry(&dst->rcu_head, dst_destroy_rcu);
 	}