netdev - [PATCH net-next 3/3] dst_cache: let rt_uncached cope with dst

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Date: Thu, 30 May 2024 19:21:03 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	David Ahern <dsahern@...nel.org>,
	Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net-next 3/3] dst_cache: let rt_uncached cope with dst_cache cleanup

Eric reported that dst_cache don't cope correctly with device removal,
keeping the cached dst unmodified even when the underlining device is
deleted and the dst itself is not uncached.

The above causes the infamous 'unregistering netdevice' hangup.

Address the issue by adding each entry held by the dst_caches to the
'uncached' list, so that the dst core will cleanup the device reference
at device removal time.

Reported-by: Eric Dumazet <edumazet@...gle.com>
Suggested-by: Eric Dumazet <edumazet@...gle.com>
Fixes: 911362c70df5 ("net: add dst_cache support")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/core/dst_cache.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/dst_cache.c b/net/core/dst_cache.c
index 6a0482e676d3..d1cb852d5748 100644
--- a/net/core/dst_cache.c
+++ b/net/core/dst_cache.c
@@ -11,6 +11,7 @@
 #include <net/route.h>
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ip6_fib.h>
+#include <net/ip6_route.h>
 #endif
 #include <uapi/linux/in.h>
 
@@ -28,6 +29,7 @@ static void dst_cache_per_cpu_dst_set(struct dst_cache_pcpu *dst_cache,
 				      struct dst_entry *dst, u32 cookie)
 {
 	dst_release(dst_cache->dst);
+
 	if (dst)
 		dst_hold(dst);
 
@@ -98,6 +100,9 @@ void dst_cache_set_ip4(struct dst_cache *dst_cache, struct dst_entry *dst,
 
 	idst = this_cpu_ptr(dst_cache->cache);
 	dst_cache_per_cpu_dst_set(idst, dst, 0);
+	if (dst && list_empty(&dst->rt_uncached))
+		rt_add_uncached_list(dst_rtable(dst));
+
 	idst->in_saddr.s_addr = saddr;
 }
 EXPORT_SYMBOL_GPL(dst_cache_set_ip4);
@@ -114,6 +119,9 @@ void dst_cache_set_ip6(struct dst_cache *dst_cache, struct dst_entry *dst,
 	idst = this_cpu_ptr(dst_cache->cache);
 	dst_cache_per_cpu_dst_set(idst, dst,
 				  rt6_get_cookie(dst_rt6_info(dst)));
+	if (dst && list_empty(&dst->rt_uncached))
+		rt6_uncached_list_add(dst_rt6_info(dst));
+
 	idst->in6_saddr = *saddr;
 }
 EXPORT_SYMBOL_GPL(dst_cache_set_ip6);
-- 
2.43.2