net: decrease cached dst counters in dst_release

Antoine Tenartrequested to merge
atenart/centos-stream-9:c9s/RHEL-83031/dst-cache into main

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

commit 3a0a3ff6593d670af2451ec363ccb7b18aec0c0a
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 ac888d58869b ("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: d71785ffc7e7 ("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

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