netdev - [PATCH 5.15.y] net: decrease cached dst counters in dst

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Message-ID: <20250520083436.1956589-1-jianqi.ren.cn@windriver.com>
Date: Tue, 20 May 2025 16:34:36 +0800
From: <jianqi.ren.cn@...driver.com>
To: <gregkh@...uxfoundation.org>, <stable@...r.kernel.org>
CC: <patches@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
        <jianqi.ren.cn@...driver.com>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <atenart@...nel.org>, <kareemem@...zon.com>, <netdev@...r.kernel.org>
Subject: [PATCH 5.15.y] net: decrease cached dst counters in dst_release

From: Antoine Tenart <atenart@...nel.org>

[ Upstream commit 3a0a3ff6593d670af2451ec363ccb7b18aec0c0a ]

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@...nel.org>
Link: https://patch.msgid.link/20250326173634.31096-1-atenart@kernel.org
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
[Minor conflict resolved due to code context change.]
Signed-off-by: Jianqi Ren <jianqi.ren.cn@...driver.com>
Signed-off-by: He Zhe <zhe.he@...driver.com>
---
Verified the build test
---
 net/core/dst.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/dst.c b/net/core/dst.c
index 6d74b4663085..c1ea331c4bfd 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -173,6 +173,14 @@ void dst_release(struct dst_entry *dst)
 			net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
 					     __func__, dst, newrefcnt);
 		if (!newrefcnt){
+#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(&dst->rcu_head, dst_destroy_rcu);
 		}
-- 
2.34.1