net: avoid to hang up on sending due to sysctl configuration overflow.

commit cdda8891 upstream.

    I found if we write a larger than 4GB value to some sysctl
variables, the sending syscall will hang up forever, because these
variables are 32 bits, such large values make them overflow to 0 or
negative.

    This patch try to fix overflow or prevent from zero value setup
of below sysctl variables:

net.core.wmem_default
net.core.rmem_default

net.core.rmem_max
net.core.wmem_max

net.ipv4.udp_rmem_min
net.ipv4.udp_wmem_min

net.ipv4.tcp_wmem
net.ipv4.tcp_rmem
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Li Yu <raise.sail@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2:
 - Adjust context
 - Delete now-unused 'zero' variable]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
(cherry picked from commit 98eee187)
[wt: backported to 2.6.32: set strategy to sysctl_intvec where relevant]
Signed-off-by: Willy Tarreau <w@1wt.eu>

net/core/sysctl_net_core.c

@@ -17,6 +17,8 @@
 static int zero = 0;
 static int ushort_max = 65535;
 
+static int one = 1;
+
 static struct ctl_table net_core_table[] = {
 #ifdef CONFIG_NET
 	{
@@ -25,7 +27,9 @@ static struct ctl_table net_core_table[] = {
 		.data		= &sysctl_wmem_max,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec_minmax,
+		.strategy	= sysctl_intvec,
+		.extra1		= &one,
 	},
 	{
 		.ctl_name	= NET_CORE_RMEM_MAX,
@@ -33,7 +37,9 @@ static struct ctl_table net_core_table[] = {
 		.data		= &sysctl_rmem_max,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec_minmax,
+		.strategy	= sysctl_intvec,
+		.extra1		= &one,
 	},
 	{
 		.ctl_name	= NET_CORE_WMEM_DEFAULT,
@@ -41,7 +47,9 @@ static struct ctl_table net_core_table[] = {
 		.data		= &sysctl_wmem_default,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec_minmax,
+		.strategy	= sysctl_intvec,
+		.extra1		= &one,
 	},
 	{
 		.ctl_name	= NET_CORE_RMEM_DEFAULT,
@@ -49,7 +57,9 @@ static struct ctl_table net_core_table[] = {
 		.data		= &sysctl_rmem_default,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec_minmax,
+		.strategy	= sysctl_intvec,
+		.extra1		= &one,
 	},
 	{
 		.ctl_name	= NET_CORE_DEV_WEIGHT,

net/ipv4/sysctl_net_ipv4.c

@@ -22,6 +22,7 @@
 #include <net/inet_frag.h>
 
 static int zero;
+static int one = 1;
 static int tcp_retr1_max = 255;
 static int tcp_syn_retries_min = 1;
 static int tcp_syn_retries_max = MAX_TCP_SYNCNT;
@@ -521,7 +522,9 @@ static struct ctl_table ipv4_table[] = {
 		.data		= &sysctl_tcp_wmem,
 		.maxlen		= sizeof(sysctl_tcp_wmem),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec_minmax,
+		.strategy	= sysctl_intvec,
+		.extra1		= &one,
 	},
 	{
 		.ctl_name	= NET_TCP_RMEM,
@@ -529,7 +532,9 @@ static struct ctl_table ipv4_table[] = {
 		.data		= &sysctl_tcp_rmem,
 		.maxlen		= sizeof(sysctl_tcp_rmem),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec_minmax,
+		.strategy	= sysctl_intvec,
+		.extra1		= &one,
 	},
 	{
 		.ctl_name	= NET_TCP_APP_WIN,
@@ -735,7 +740,7 @@ static struct ctl_table ipv4_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
 		.strategy	= sysctl_intvec,
-		.extra1		= &zero
+		.extra1		= &one
 	},
 	{
 		.ctl_name	= CTL_UNNUMBERED,
@@ -745,7 +750,7 @@ static struct ctl_table ipv4_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
 		.strategy	= sysctl_intvec,
-		.extra1		= &zero
+		.extra1		= &one
 	},
 	{ .ctl_name = 0 }
 };