Re: Linux 4.14.127

[Greg KH]

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 828fcd6711b3..3bbe6fb2b086 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -241,6 +241,14 @@ tcp_base_mss - INTEGER
 	Path MTU discovery (MTU probing).  If MTU probing is enabled,
 	this is the initial MSS used by the connection.
 
+tcp_min_snd_mss - INTEGER
+	TCP SYN and SYNACK messages usually advertise an ADVMSS option,
+	as described in RFC 1122 and RFC 6691.
+	If this ADVMSS option is smaller than tcp_min_snd_mss,
+	it is silently capped to tcp_min_snd_mss.
+
+	Default : 48 (at least 8 bytes of payload per segment)
+
 tcp_congestion_control - STRING
 	Set the congestion control algorithm to be used for new
 	connections. The algorithm "reno" is always available, but
diff --git a/Makefile b/Makefile
index 631f8a8e28e0..330f23238005 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 VERSION = 4
 PATCHLEVEL = 14
-SUBLEVEL = 126
+SUBLEVEL = 127
 EXTRAVERSION =
 NAME = Petit Gorille
 
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index fe322fa611e6..60aea230dc6a 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -450,4 +450,8 @@ static inline u16 tcp_mss_clamp(const struct tcp_sock *tp, u16 mss)
 
 	return (user_mss && user_mss < mss) ? user_mss : mss;
 }
+
+int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from, int pcount,
+		  int shiftlen);
+
 #endif	/* _LINUX_TCP_H */
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index a2e4adafd34d..e268c970ec54 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -107,6 +107,7 @@ struct netns_ipv4 {
 #endif
 	int sysctl_tcp_mtu_probing;
 	int sysctl_tcp_base_mss;
+	int sysctl_tcp_min_snd_mss;
 	int sysctl_tcp_probe_threshold;
 	u32 sysctl_tcp_probe_interval;
 
diff --git a/include/net/tcp.h b/include/net/tcp.h
index d0c2dbe94e21..1179ef4f0768 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -57,6 +57,8 @@ void tcp_time_wait(struct sock *sk, int state, int timeo);
 
 #define MAX_TCP_HEADER	(128 + MAX_HEADER)
 #define MAX_TCP_OPTION_SPACE 40
+#define TCP_MIN_SND_MSS		48
+#define TCP_MIN_GSO_SIZE	(TCP_MIN_SND_MSS - MAX_TCP_OPTION_SPACE)
 
 /*
  * Never offer a window over 32767 without using window scaling. Some
diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index f5d753e60836..bf31965355c6 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -278,6 +278,7 @@ enum
 	LINUX_MIB_TCPKEEPALIVE,			/* TCPKeepAlive */
 	LINUX_MIB_TCPMTUPFAIL,			/* TCPMTUPFail */
 	LINUX_MIB_TCPMTUPSUCCESS,		/* TCPMTUPSuccess */
+	LINUX_MIB_TCPWQUEUETOOBIG,		/* TCPWqueueTooBig */
 	__LINUX_MIB_MAX
 };
 
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 3fbf688a1943..88aaf14983e8 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -299,6 +299,7 @@ static const struct snmp_mib snmp4_net_list[] = {
 	SNMP_MIB_ITEM("TCPKeepAlive", LINUX_MIB_TCPKEEPALIVE),
 	SNMP_MIB_ITEM("TCPMTUPFail", LINUX_MIB_TCPMTUPFAIL),
 	SNMP_MIB_ITEM("TCPMTUPSuccess", LINUX_MIB_TCPMTUPSUCCESS),
+	SNMP_MIB_ITEM("TCPWqueueTooBig", LINUX_MIB_TCPWQUEUETOOBIG),
 	SNMP_MIB_SENTINEL
 };
 
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index e8caab8e2f5c..78771272f613 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -37,6 +37,8 @@ static int ip_local_port_range_min[] = { 1, 1 };
 static int ip_local_port_range_max[] = { 65535, 65535 };
 static int tcp_adv_win_scale_min = -31;
 static int tcp_adv_win_scale_max = 31;
+static int tcp_min_snd_mss_min = TCP_MIN_SND_MSS;
+static int tcp_min_snd_mss_max = 65535;
 static int ip_privileged_port_min;
 static int ip_privileged_port_max = 65535;
 static int ip_ttl_min = 1;
@@ -943,6 +945,15 @@ static struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
 	},
+	{
+		.procname	= "tcp_min_snd_mss",
+		.data		= &init_net.ipv4.sysctl_tcp_min_snd_mss,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &tcp_min_snd_mss_min,
+		.extra2		= &tcp_min_snd_mss_max,
+	},
 	{
 		.procname	= "tcp_probe_threshold",
 		.data		= &init_net.ipv4.sysctl_tcp_probe_threshold,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 00ae9a1d44ed..d51571be9eac 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3480,6 +3480,7 @@ void __init tcp_init(void)
 	unsigned long limit;
 	unsigned int i;
 
+	BUILD_BUG_ON(TCP_MIN_SND_MSS <= MAX_TCP_OPTION_SPACE);
 	BUILD_BUG_ON(sizeof(struct tcp_skb_cb) >
 		     FIELD_SIZEOF(struct sk_buff, cb));
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 657d33e2ff6a..8e080f3b75bd 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1329,7 +1329,7 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
 	TCP_SKB_CB(skb)->seq += shifted;
 
 	tcp_skb_pcount_add(prev, pcount);
-	BUG_ON(tcp_skb_pcount(skb) < pcount);
+	WARN_ON_ONCE(tcp_skb_pcount(skb) < pcount);
 	tcp_skb_pcount_add(skb, -pcount);
 
 	/* When we're adding to gso_segs == 1, gso_size will be zero,
@@ -1396,6 +1396,21 @@ static int skb_can_shift(const struct sk_buff *skb)
 	return !skb_headlen(skb) && skb_is_nonlinear(skb);
 }
 
+int tcp_skb_shift(struct sk_buff *to, struct sk_buff *from,
+		  int pcount, int shiftlen)
+{
+	/* TCP min gso_size is 8 bytes (TCP_MIN_GSO_SIZE)
+	 * Since TCP_SKB_CB(skb)->tcp_gso_segs is 16 bits, we need
+	 * to make sure not storing more than 65535 * 8 bytes per skb,
+	 * even if current MSS is bigger.
+	 */
+	if (unlikely(to->len + shiftlen >= 65535 * TCP_MIN_GSO_SIZE))
+		return 0;
+	if (unlikely(tcp_skb_pcount(to) + pcount > 65535))
+		return 0;
+	return skb_shift(to, from, shiftlen);
+}
+
 /* Try collapsing SACK blocks spanning across multiple skbs to a single
  * skb.
  */
@@ -1407,6 +1422,7 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *prev;
 	int mss;
+	int next_pcount;
 	int pcount = 0;
 	int len;
 	int in_sack;
@@ -1504,7 +1520,7 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 	if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una))
 		goto fallback;
 
-	if (!skb_shift(prev, skb, len))
+	if (!tcp_skb_shift(prev, skb, pcount, len))
 		goto fallback;
 	if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))
 		goto out;
@@ -1523,11 +1539,11 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
 		goto out;
 
 	len = skb->len;
-	if (skb_shift(prev, skb, len)) {
-		pcount += tcp_skb_pcount(skb);
-		tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0);
+	next_pcount = tcp_skb_pcount(skb);
+	if (tcp_skb_shift(prev, skb, next_pcount, len)) {
+		pcount += next_pcount;
+		tcp_shifted_skb(sk, skb, state, next_pcount, len, mss, 0);
 	}
-
 out:
 	state->fack_count += pcount;
 	return prev;
@@ -2810,9 +2826,9 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 	bool do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) &&
 				    (tcp_fackets_out(tp) > tp->reordering));
 
-	if (WARN_ON(!tp->packets_out && tp->sacked_out))
+	if (!tp->packets_out && tp->sacked_out)
 		tp->sacked_out = 0;
-	if (WARN_ON(!tp->sacked_out && tp->fackets_out))
+	if (!tp->sacked_out && tp->fackets_out)
 		tp->fackets_out = 0;
 
 	/* Now state machine starts.
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 97a414dbdaf4..0569718e3656 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2477,6 +2477,7 @@ static int __net_init tcp_sk_init(struct net *net)
 	net->ipv4.sysctl_tcp_ecn_fallback = 1;
 
 	net->ipv4.sysctl_tcp_base_mss = TCP_BASE_MSS;
+	net->ipv4.sysctl_tcp_min_snd_mss = TCP_MIN_SND_MSS;
 	net->ipv4.sysctl_tcp_probe_threshold = TCP_PROBE_THRESHOLD;
 	net->ipv4.sysctl_tcp_probe_interval = TCP_PROBE_INTERVAL;
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 24bad638c2ec..a8772e11dc1c 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1274,6 +1274,11 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
 	if (nsize < 0)
 		nsize = 0;
 
+	if (unlikely((sk->sk_wmem_queued >> 1) > sk->sk_sndbuf)) {
+		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG);
+		return -ENOMEM;
+	}
+
 	if (skb_unclone(skb, gfp))
 		return -ENOMEM;
 
@@ -1442,8 +1447,7 @@ static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu)
 	mss_now -= icsk->icsk_ext_hdr_len;
 
 	/* Then reserve room for full set of TCP options and 8 bytes of data */
-	if (mss_now < 48)
-		mss_now = 48;
+	mss_now = max(mss_now, sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss);
 	return mss_now;
 }
 
@@ -2724,7 +2728,7 @@ static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
 		if (next_skb_size <= skb_availroom(skb))
 			skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size),
 				      next_skb_size);
-		else if (!skb_shift(skb, next_skb, next_skb_size))
+		else if (!tcp_skb_shift(skb, next_skb, 1, next_skb_size))
 			return false;
 	}
 	tcp_highest_sack_replace(sk, next_skb, skb);
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index a845b7692c1b..592d6e9967a9 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -141,6 +141,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
 			mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
 			mss = min(net->ipv4.sysctl_tcp_base_mss, mss);
 			mss = max(mss, 68 - tp->tcp_header_len);
+			mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss);
 			icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
 			tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 		}