4.4-stable review patch. If anyone has any objections, please let me know.
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From: Jason Baron jbaron@akamai.com
[ Upstream commit 56d806222ace4c3aeae516cd7a855340fb2839d8 ]
sock_reset_flag() maps to __clear_bit() not the atomic version clear_bit(). Thus, we need smp_mb(), smp_mb__after_atomic() is not sufficient.
Fixes: 3c7151275c0c ("tcp: add memory barriers to write space paths") Cc: Eric Dumazet eric.dumazet@gmail.com Cc: Oleg Nesterov oleg@redhat.com Signed-off-by: Jason Baron jbaron@akamai.com Acked-by: Eric Dumazet edumazet@google.com Reported-by: Oleg Nesterov oleg@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/tcp_input.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -4942,7 +4942,7 @@ static void tcp_check_space(struct sock if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); /* pairs with tcp_poll() */ - smp_mb__after_atomic(); + smp_mb(); if (sk->sk_socket && test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) tcp_new_space(sk);