netdev.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Eric Dumazet <edumazet@google.com>
To: "David S . Miller" <davem@davemloft.net>
Cc: netdev <netdev@vger.kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	Eric Dumazet <eric.dumazet@gmail.com>,
	Jakub Kicinski <jakub.kicinski@netronome.com>
Subject: [PATCH net 8/9] tcp: annotate sk->sk_sndbuf lockless reads
Date: Thu, 10 Oct 2019 20:17:45 -0700	[thread overview]
Message-ID: <20191011031746.16220-9-edumazet@google.com> (raw)
In-Reply-To: <20191011031746.16220-1-edumazet@google.com>

For the sake of tcp_poll(), there are few places where we fetch
sk->sk_sndbuf 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>
---
 include/net/sock.h   | 18 +++++++++++-------
 net/core/filter.c    |  3 ++-
 net/core/sock.c      | 15 +++++++++------
 net/ipv4/tcp.c       |  2 +-
 net/ipv4/tcp_input.c |  3 ++-
 5 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 79f54e1f88277dc7cc64ca0f35fd5ba869a2f96d..3d1e7502333e7ea0ff866f8982048800193caf33 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -883,7 +883,7 @@ static inline int sk_stream_min_wspace(const struct sock *sk)
 
 static inline int sk_stream_wspace(const struct sock *sk)
 {
-	return sk->sk_sndbuf - sk->sk_wmem_queued;
+	return READ_ONCE(sk->sk_sndbuf) - sk->sk_wmem_queued;
 }
 
 void sk_stream_write_space(struct sock *sk);
@@ -1207,7 +1207,7 @@ static inline void sk_refcnt_debug_release(const struct sock *sk)
 
 static inline bool __sk_stream_memory_free(const struct sock *sk, int wake)
 {
-	if (sk->sk_wmem_queued >= sk->sk_sndbuf)
+	if (sk->sk_wmem_queued >= READ_ONCE(sk->sk_sndbuf))
 		return false;
 
 	return sk->sk_prot->stream_memory_free ?
@@ -2220,10 +2220,14 @@ static inline void sk_wake_async(const struct sock *sk, int how, int band)
 
 static inline void sk_stream_moderate_sndbuf(struct sock *sk)
 {
-	if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) {
-		sk->sk_sndbuf = min(sk->sk_sndbuf, sk->sk_wmem_queued >> 1);
-		sk->sk_sndbuf = max_t(u32, sk->sk_sndbuf, SOCK_MIN_SNDBUF);
-	}
+	u32 val;
+
+	if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
+		return;
+
+	val = min(sk->sk_sndbuf, sk->sk_wmem_queued >> 1);
+
+	WRITE_ONCE(sk->sk_sndbuf, max_t(u32, val, SOCK_MIN_SNDBUF));
 }
 
 struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp,
@@ -2251,7 +2255,7 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag);
  */
 static inline bool sock_writeable(const struct sock *sk)
 {
-	return refcount_read(&sk->sk_wmem_alloc) < (sk->sk_sndbuf >> 1);
+	return refcount_read(&sk->sk_wmem_alloc) < (READ_ONCE(sk->sk_sndbuf) >> 1);
 }
 
 static inline gfp_t gfp_any(void)
diff --git a/net/core/filter.c b/net/core/filter.c
index 7deceaeeed7bace2bb805d110190b98819cfc7b1..3fed5755494bd39cf55ca1806ead67609ae8b587 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4258,7 +4258,8 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
 		case SO_SNDBUF:
 			val = min_t(u32, val, sysctl_wmem_max);
 			sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
-			sk->sk_sndbuf = max_t(int, val * 2, SOCK_MIN_SNDBUF);
+			WRITE_ONCE(sk->sk_sndbuf,
+				   max_t(int, val * 2, SOCK_MIN_SNDBUF));
 			break;
 		case SO_MAX_PACING_RATE: /* 32bit version */
 			if (val != ~0U)
diff --git a/net/core/sock.c b/net/core/sock.c
index 8c8f61e70141583afe52420b58fea4bcce3a74f0..cd075bc86407a5816bd448521955525ebe941694 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -785,7 +785,8 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 		 */
 		val = min_t(int, val, INT_MAX / 2);
 		sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
-		sk->sk_sndbuf = max_t(int, val * 2, SOCK_MIN_SNDBUF);
+		WRITE_ONCE(sk->sk_sndbuf,
+			   max_t(int, val * 2, SOCK_MIN_SNDBUF));
 		/* Wake up sending tasks if we upped the value. */
 		sk->sk_write_space(sk);
 		break;
@@ -2089,8 +2090,10 @@ EXPORT_SYMBOL(sock_i_ino);
 struct sk_buff *sock_wmalloc(struct sock *sk, unsigned long size, int force,
 			     gfp_t priority)
 {
-	if (force || refcount_read(&sk->sk_wmem_alloc) < sk->sk_sndbuf) {
+	if (force ||
+	    refcount_read(&sk->sk_wmem_alloc) < READ_ONCE(sk->sk_sndbuf)) {
 		struct sk_buff *skb = alloc_skb(size, priority);
+
 		if (skb) {
 			skb_set_owner_w(skb, sk);
 			return skb;
@@ -2191,7 +2194,7 @@ static long sock_wait_for_wmem(struct sock *sk, long timeo)
 			break;
 		set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
-		if (refcount_read(&sk->sk_wmem_alloc) < sk->sk_sndbuf)
+		if (refcount_read(&sk->sk_wmem_alloc) < READ_ONCE(sk->sk_sndbuf))
 			break;
 		if (sk->sk_shutdown & SEND_SHUTDOWN)
 			break;
@@ -2226,7 +2229,7 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
 		if (sk->sk_shutdown & SEND_SHUTDOWN)
 			goto failure;
 
-		if (sk_wmem_alloc_get(sk) < sk->sk_sndbuf)
+		if (sk_wmem_alloc_get(sk) < READ_ONCE(sk->sk_sndbuf))
 			break;
 
 		sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
@@ -2807,7 +2810,7 @@ static void sock_def_write_space(struct sock *sk)
 	/* Do not wake up a writer until he can make "significant"
 	 * progress.  --DaveM
 	 */
-	if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf) {
+	if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= READ_ONCE(sk->sk_sndbuf)) {
 		wq = rcu_dereference(sk->sk_wq);
 		if (skwq_has_sleeper(wq))
 			wake_up_interruptible_sync_poll(&wq->wait, EPOLLOUT |
@@ -3207,7 +3210,7 @@ void sk_get_meminfo(const struct sock *sk, u32 *mem)
 	mem[SK_MEMINFO_RMEM_ALLOC] = sk_rmem_alloc_get(sk);
 	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_SNDBUF] = READ_ONCE(sk->sk_sndbuf);
 	mem[SK_MEMINFO_FWD_ALLOC] = sk->sk_forward_alloc;
 	mem[SK_MEMINFO_WMEM_QUEUED] = sk->sk_wmem_queued;
 	mem[SK_MEMINFO_OPTMEM] = atomic_read(&sk->sk_omem_alloc);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index bc0481aa6633c0c871c57a89d38ef57734b51f12..11185326297211bee3746edd725d106643b78720 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -450,7 +450,7 @@ 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];
+	WRITE_ONCE(sk->sk_sndbuf, sock_net(sk)->ipv4.sysctl_tcp_wmem[1]);
 	WRITE_ONCE(sk->sk_rcvbuf, sock_net(sk)->ipv4.sysctl_tcp_rmem[1]);
 
 	sk_sockets_allocated_inc(sk);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6995df20710a7bf48d9aca88c14e5980f4fc9615..a2e52ad7cdab3e66a469a8ca850848988b3888d7 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -359,7 +359,8 @@ static void tcp_sndbuf_expand(struct sock *sk)
 	sndmem *= nr_segs * per_mss;
 
 	if (sk->sk_sndbuf < sndmem)
-		sk->sk_sndbuf = min(sndmem, sock_net(sk)->ipv4.sysctl_tcp_wmem[2]);
+		WRITE_ONCE(sk->sk_sndbuf,
+			   min(sndmem, sock_net(sk)->ipv4.sysctl_tcp_wmem[2]));
 }
 
 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
-- 
2.23.0.700.g56cf767bdb-goog


  parent reply	other threads:[~2019-10-11  3:18 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-11  3:17 [PATCH net 0/9] tcp: address KCSAN reports in tcp_poll() (part I) Eric Dumazet
2019-10-11  3:17 ` [PATCH net 1/9] tcp: add rcu protection around tp->fastopen_rsk Eric Dumazet
2019-10-11  3:17 ` [PATCH net 2/9] tcp: annotate tp->rcv_nxt lockless reads Eric Dumazet
2019-10-11  3:17 ` [PATCH net 3/9] tcp: annotate tp->copied_seq " Eric Dumazet
2019-10-11  3:17 ` [PATCH net 4/9] tcp: annotate tp->write_seq " Eric Dumazet
2019-10-11  3:17 ` [PATCH net 5/9] tcp: annotate tp->snd_nxt " Eric Dumazet
2019-10-11  3:17 ` [PATCH net 6/9] tcp: annotate tp->urg_seq " Eric Dumazet
2019-10-11  3:17 ` [PATCH net 7/9] tcp: annotate sk->sk_rcvbuf " Eric Dumazet
2019-10-11  3:17 ` Eric Dumazet [this message]
2019-10-11  3:17 ` [PATCH net 9/9] tcp: annotate sk->sk_wmem_queued " Eric Dumazet
2019-10-13 17:13 ` [PATCH net 0/9] tcp: address KCSAN reports in tcp_poll() (part I) David Miller

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191011031746.16220-9-edumazet@google.com \
    --to=edumazet@google.com \
    --cc=davem@davemloft.net \
    --cc=eric.dumazet@gmail.com \
    --cc=jakub.kicinski@netronome.com \
    --cc=netdev@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).