raw: Fix a data-race around sysctl_raw_l3mdev_accept.

stable inclusion
from stable-v5.10.132
commit 038a87b3e460d2ee579c8b1bd3890d816d6687b1
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5YS3T

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=038a87b3e460d2ee579c8b1bd3890d816d6687b1



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[ Upstream commit 1dace014 ]

While reading sysctl_raw_l3mdev_accept, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 6897445f ("net: provide a sysctl raw_l3mdev_accept for raw socket lookup with VRFs")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>