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Commit ebb3b78d authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: annotate sk->sk_rcvbuf lockless reads 



For the sake of tcp_poll(), there are few places where we fetch
sk->sk_rcvbuf while this field can change from IRQ or other cpu.

We need to add READ_ONCE() annotations, and also make sure write
sides use corresponding WRITE_ONCE() to avoid store-tearing.

Note that other transports probably need similar fixes.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d9b55bf7

include/net/tcp.h

+2 −2
Original line number Diff line number Diff line
@@ -1380,14 +1380,14 @@ static inline int tcp_win_from_space(const struct sock *sk, int space) 
/* Note: caller must be prepared to deal with negative returns */

static inline int tcp_space(const struct sock *sk)

{

	return tcp_win_from_space(sk, sk->sk_rcvbuf -

	return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf) -

				  READ_ONCE(sk->sk_backlog.len) -

				  atomic_read(&sk->sk_rmem_alloc));

}



static inline int tcp_full_space(const struct sock *sk)

{

	return tcp_win_from_space(sk, sk->sk_rcvbuf);

	return tcp_win_from_space(sk, READ_ONCE(sk->sk_rcvbuf));

}



extern void tcp_openreq_init_rwin(struct request_sock *req,

include/trace/events/sock.h

+1 −1
Original line number Diff line number Diff line
@@ -82,7 +82,7 @@ TRACE_EVENT(sock_rcvqueue_full, 
	TP_fast_assign(

		__entry->rmem_alloc = atomic_read(&sk->sk_rmem_alloc);

		__entry->truesize   = skb->truesize;

		__entry->sk_rcvbuf  = sk->sk_rcvbuf;

		__entry->sk_rcvbuf  = READ_ONCE(sk->sk_rcvbuf);

	),



	TP_printk("rmem_alloc=%d truesize=%u sk_rcvbuf=%d",

net/core/filter.c

+2 −1
Original line number Diff line number Diff line
@@ -4252,7 +4252,8 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock, 
		case SO_RCVBUF:

			val = min_t(u32, val, sysctl_rmem_max);

			sk->sk_userlocks |= SOCK_RCVBUF_LOCK;

			sk->sk_rcvbuf = max_t(int, val * 2, SOCK_MIN_RCVBUF);

			WRITE_ONCE(sk->sk_rcvbuf,

				   max_t(int, val * 2, SOCK_MIN_RCVBUF));

			break;

		case SO_SNDBUF:

			val = min_t(u32, val, sysctl_wmem_max);

net/core/skbuff.c

+1 −1
Original line number Diff line number Diff line
@@ -4415,7 +4415,7 @@ static void skb_set_err_queue(struct sk_buff *skb) 
int sock_queue_err_skb(struct sock *sk, struct sk_buff *skb)

{

	if (atomic_read(&sk->sk_rmem_alloc) + skb->truesize >=

	    (unsigned int)sk->sk_rcvbuf)

	    (unsigned int)READ_ONCE(sk->sk_rcvbuf))

		return -ENOMEM;



	skb_orphan(skb);

net/core/sock.c

+3 −2
Original line number Diff line number Diff line
@@ -831,7 +831,8 @@ int sock_setsockopt(struct socket *sock, int level, int optname, 
		 * returning the value we actually used in getsockopt

		 * is the most desirable behavior.

		 */

		sk->sk_rcvbuf = max_t(int, val * 2, SOCK_MIN_RCVBUF);

		WRITE_ONCE(sk->sk_rcvbuf,

			   max_t(int, val * 2, SOCK_MIN_RCVBUF));

		break;



	case SO_RCVBUFFORCE:
@@ -3204,7 +3205,7 @@ void sk_get_meminfo(const struct sock *sk, u32 *mem) 
	memset(mem, 0, sizeof(*mem) * SK_MEMINFO_VARS);



	mem[SK_MEMINFO_RMEM_ALLOC] = sk_rmem_alloc_get(sk);

	mem[SK_MEMINFO_RCVBUF] = sk->sk_rcvbuf;

	mem[SK_MEMINFO_RCVBUF] = READ_ONCE(sk->sk_rcvbuf);

	mem[SK_MEMINFO_WMEM_ALLOC] = sk_wmem_alloc_get(sk);

	mem[SK_MEMINFO_SNDBUF] = sk->sk_sndbuf;

	mem[SK_MEMINFO_FWD_ALLOC] = sk->sk_forward_alloc;