ip: Fix a data-race around sysctl_fwmark_reflect.

stable inclusion
from stable-v5.10.134
commit 0ee76fe01ff3c0b4efaa500aecc90d7c8d3a8860
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5ZVR7

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=0ee76fe01ff3c0b4efaa500aecc90d7c8d3a8860

--------------------------------

[ Upstream commit 85d0b4db ]

While reading sysctl_fwmark_reflect, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: e110861f ("net: add a sysctl to reflect the fwmark on replies")
Signed-off-by: NKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>

include/net/ip.h

@@ -382,7 +382,7 @@ void ipfrag_init(void);
 void ip_static_sysctl_init(void);
 
 #define IP4_REPLY_MARK(net, mark) \
-	((net)->ipv4.sysctl_fwmark_reflect ? (mark) : 0)
+	(READ_ONCE((net)->ipv4.sysctl_fwmark_reflect) ? (mark) : 0)
 
 static inline bool ip_is_fragment(const struct iphdr *iph)
 {