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Commit 8f8e806c authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman
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net: annotate lockless accesses to sk->sk_pacing_shift 



[ Upstream commit 7c68fa2bddda6d942bd387c9ba5b4300737fd991 ]

sk->sk_pacing_shift can be read and written without lock
synchronization. This patch adds annotations to
document this fact and avoid future syzbot complains.

This might also avoid unexpected false sharing
in sk_pacing_shift_update(), as the compiler
could remove the conditional check and always
write over sk->sk_pacing_shift :

if (sk->sk_pacing_shift != val)
	sk->sk_pacing_shift = val;

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 2c446b34

include/net/sock.h

+2 −2
Original line number Diff line number Diff line
@@ -2589,9 +2589,9 @@ static inline int sk_get_rmem0(const struct sock *sk, const struct proto *proto) 
 */

static inline void sk_pacing_shift_update(struct sock *sk, int val)

{

	if (!sk || !sk_fullsock(sk) || sk->sk_pacing_shift == val)

	if (!sk || !sk_fullsock(sk) || READ_ONCE(sk->sk_pacing_shift) == val)

		return;

	sk->sk_pacing_shift = val;

	WRITE_ONCE(sk->sk_pacing_shift, val);

}



/* if a socket is bound to a device, check that the given device

net/core/sock.c

+1 −1
Original line number Diff line number Diff line
@@ -2918,7 +2918,7 @@ void sock_init_data(struct socket *sock, struct sock *sk) 


	sk->sk_max_pacing_rate = ~0UL;

	sk->sk_pacing_rate = ~0UL;

	sk->sk_pacing_shift = 10;

	WRITE_ONCE(sk->sk_pacing_shift, 10);

	sk->sk_incoming_cpu = -1;



	sk_rx_queue_clear(sk);

net/ipv4/tcp_bbr.c

+2 −1
Original line number Diff line number Diff line
@@ -306,7 +306,8 @@ static u32 bbr_tso_segs_goal(struct sock *sk) 
	/* Sort of tcp_tso_autosize() but ignoring

	 * driver provided sk_gso_max_size.

	 */

	bytes = min_t(unsigned long, sk->sk_pacing_rate >> sk->sk_pacing_shift,

	bytes = min_t(unsigned long,

		      sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift),

		      GSO_MAX_SIZE - 1 - MAX_TCP_HEADER);

	segs = max_t(u32, bytes / tp->mss_cache, bbr_min_tso_segs(sk));

net/ipv4/tcp_output.c

+2 −2
Original line number Diff line number Diff line
@@ -1728,7 +1728,7 @@ static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now, 
	u32 bytes, segs;



	bytes = min_t(unsigned long,

		      sk->sk_pacing_rate >> sk->sk_pacing_shift,

		      sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift),

		      sk->sk_gso_max_size - 1 - MAX_TCP_HEADER);



	/* Goal is to send at least one packet per ms,
@@ -2263,7 +2263,7 @@ static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb, 


	limit = max_t(unsigned long,

		      2 * skb->truesize,

		      sk->sk_pacing_rate >> sk->sk_pacing_shift);

		      sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift));

	if (sk->sk_pacing_status == SK_PACING_NONE)

		limit = min_t(unsigned long, limit,

			      sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes);