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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: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2019-10-10 20:17:44 -07:00 committed by David S. Miller
parent d9b55bf7b6
commit ebb3b78db7
7 changed files with 15 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/net/tcp.h
View File

@ -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,

2
include/trace/events/sock.h
View File

@ -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",

3
net/core/filter.c
View File

@ -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);

2
net/core/skbuff.c
View File

@ -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);

5
net/core/sock.c
View File

@ -831,7 +831,8 @@ set_rcvbuf:
* 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;

4
net/ipv4/tcp.c
View File

@ -451,7 +451,7 @@ void tcp_init_sock(struct sock *sk)
icsk->icsk_sync_mss = tcp_sync_mss;
sk->sk_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[1];
sk->sk_rcvbuf = sock_net(sk)->ipv4.sysctl_tcp_rmem[1];
WRITE_ONCE(sk->sk_rcvbuf, sock_net(sk)->ipv4.sysctl_tcp_rmem[1]);
sk_sockets_allocated_inc(sk);
sk->sk_route_forced_caps = NETIF_F_GSO;
@ -1711,7 +1711,7 @@ int tcp_set_rcvlowat(struct sock *sk, int val)
val <<= 1;
if (val > sk->sk_rcvbuf) {
sk->sk_rcvbuf = val;
WRITE_ONCE(sk->sk_rcvbuf, val);
tcp_sk(sk)->window_clamp = tcp_win_from_space(sk, val);
}
return 0;

7
net/ipv4/tcp_input.c
View File

@ -483,8 +483,9 @@ static void tcp_clamp_window(struct sock *sk)
!(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
!tcp_under_memory_pressure(sk) &&
sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) {
sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
net->ipv4.sysctl_tcp_rmem[2]);
WRITE_ONCE(sk->sk_rcvbuf,
min(atomic_read(&sk->sk_rmem_alloc),
net->ipv4.sysctl_tcp_rmem[2]));
}
if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf)
tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss);
@ -648,7 +649,7 @@ void tcp_rcv_space_adjust(struct sock *sk)
rcvbuf = min_t(u64, rcvwin * rcvmem,
sock_net(sk)->ipv4.sysctl_tcp_rmem[2]);
if (rcvbuf > sk->sk_rcvbuf) {
sk->sk_rcvbuf = rcvbuf;
WRITE_ONCE(sk->sk_rcvbuf, rcvbuf);
/* Make the window clamp follow along. */
tp->window_clamp = tcp_win_from_space(sk, rcvbuf);