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

    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>

2 files changed, 17 insertions, 8 deletions

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index d1b08045a9df..cfdb46ab3a7f 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -20,6 +20,8 @@
 #include <net/sock.h>
 #include <net/net_ratelimit.h>
 
+static int one = 1;
+
 #ifdef CONFIG_RPS
 static int rps_sock_flow_sysctl(ctl_table *table, int write,
                                 void __user *buffer, size_t *lenp, loff_t *ppos)
@@ -92,28 +94,32 @@ 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,
+                .extra1         = &one,
         },
         {
                 .procname       = "rmem_max",
                 .data           = &sysctl_rmem_max,
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
-                .proc_handler   = proc_dointvec
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = &one,
         },
         {
                 .procname       = "wmem_default",
                 .data           = &sysctl_wmem_default,
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
-                .proc_handler   = proc_dointvec
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = &one,
         },
         {
                 .procname       = "rmem_default",
                 .data           = &sysctl_rmem_default,
                 .maxlen         = sizeof(int),
                 .mode           = 0644,
-                .proc_handler   = proc_dointvec
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = &one,
         },
         {
                 .procname       = "dev_weight",
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index a25e1d286b99..2622707602d1 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -27,6 +27,7 @@
 #include <net/tcp_memcontrol.h>
 
 static int zero;
+static int one = 1;
 static int two = 2;
 static int tcp_retr1_max = 255;
 static int ip_local_port_range_min[] = { 1, 1 };
@@ -549,14 +550,16 @@ 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,
+                .extra1         = &one,
         },
         {
                 .procname       = "tcp_rmem",
                 .data           = &sysctl_tcp_rmem,
                 .maxlen         = sizeof(sysctl_tcp_rmem),
                 .mode           = 0644,
-                .proc_handler   = proc_dointvec
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = &one,
         },
         {
                 .procname       = "tcp_app_win",
@@ -779,7 +782,7 @@ static struct ctl_table ipv4_table[] = {
                 .maxlen         = sizeof(sysctl_udp_rmem_min),
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec_minmax,
-                .extra1         = &zero
+                .extra1         = &one
         },
         {
                 .procname       = "udp_wmem_min",
@@ -787,7 +790,7 @@ static struct ctl_table ipv4_table[] = {
                 .maxlen         = sizeof(sysctl_udp_wmem_min),
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec_minmax,
-                .extra1         = &zero
+                .extra1         = &one
         },
         { }
 };