linux-kernel - [PATCH] ipv6: Use local variable for ifa->flags in inet6_fill

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Message-Id: <20241104132434.3101812-1-zilinguan811@gmail.com>
Date: Mon,  4 Nov 2024 13:24:34 +0000
From: Zilin Guan <zilinguan811@...il.com>
To: davem@...emloft.net
Cc: dsahern@...nel.org,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	horms@...nel.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Zilin Guan <zilinguan811@...il.com>
Subject: [PATCH] ipv6: Use local variable for ifa->flags in inet6_fill_ifaddr

Currently, the inet6_fill_ifaddr() function reads the value of ifa->flags
using READ_ONCE() and stores it in the local variable flags. However,
the subsequent call to put_ifaddrmsg() uses ifa->flags again instead of
the already read local variable. This re-read is unnecessary because
no other thread can modify ifa->flags between the initial READ_ONCE()
and the subsequent use in put_ifaddrmsg().

Signed-off-by: Zilin Guan <zilinguan811@...il.com>
---
 net/ipv6/addrconf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 94dceac52884..c4b080471b39 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5143,7 +5143,7 @@ static int inet6_fill_ifaddr(struct sk_buff *skb,
 		return -EMSGSIZE;
 
 	flags = READ_ONCE(ifa->flags);
-	put_ifaddrmsg(nlh, ifa->prefix_len, ifa->flags, rt_scope(ifa->scope),
+	put_ifaddrmsg(nlh, ifa->prefix_len, flags, rt_scope(ifa->scope),
 		      ifa->idev->dev->ifindex);
 
 	if (args->netnsid >= 0 &&
-- 
2.34.1