net: Fix sysctl restarts...

Yuck.  It turns out that when we restart sysctls we were restarting
with the values already changed.  Which unfortunately meant that
the second time through we thought there was no change and skipped
all kinds of work, despite the fact that there was indeed a change.

I have fixed this the simplest way possible by restoring the changed
values when we restart the sysctl write.

One of my coworkers spotted this bug when after disabling forwarding
on an interface pings were still forwarded.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 040c4f05b65321b6b2c6023bb0eba66eecb7c26a..26dec2be96152aa88b3b8893f1fe175a9eb8a418 100644 (file)
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1317,14 +1317,19 @@ static int devinet_sysctl_forward(ctl_table *ctl, int write,
 {
        int *valp = ctl->data;
        int val = *valp;
+       loff_t pos = *ppos;
        int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
 
        if (write && *valp != val) {
                struct net *net = ctl->extra2;
 
                if (valp != &IPV4_DEVCONF_DFLT(net, FORWARDING)) {
-                       if (!rtnl_trylock())
+                       if (!rtnl_trylock()) {
+                               /* Restore the original values before restarting */
+                               *valp = val;
+                               *ppos = pos;
                                return restart_syscall();
+                       }
                        if (valp == &IPV4_DEVCONF_ALL(net, FORWARDING)) {
                                inet_forward_change(net);
                        } else if (*valp) {

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index de7a194a64ab4fa0cf864d1fe3f83a3974e3b727..143791da062c5118656f826033bb673435ab09f2 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -502,8 +502,11 @@ static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int old)
        if (p == &net->ipv6.devconf_dflt->forwarding)
                return 0;
 
-       if (!rtnl_trylock())
+       if (!rtnl_trylock()) {
+               /* Restore the original values before restarting */
+               *p = old;
                return restart_syscall();
+       }
 
        if (p == &net->ipv6.devconf_all->forwarding) {
                __s32 newf = net->ipv6.devconf_all->forwarding;
@@ -4028,12 +4031,15 @@ int addrconf_sysctl_forward(ctl_table *ctl, int write,
 {
        int *valp = ctl->data;
        int val = *valp;
+       loff_t pos = *ppos;
        int ret;
 
        ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
 
        if (write)
                ret = addrconf_fixup_forwarding(ctl, valp, val);
+       if (ret)
+               *ppos = pos;
        return ret;
 }
 
@@ -4075,8 +4081,11 @@ static int addrconf_disable_ipv6(struct ctl_table *table, int *p, int old)
        if (p == &net->ipv6.devconf_dflt->disable_ipv6)
                return 0;
 
-       if (!rtnl_trylock())
+       if (!rtnl_trylock()) {
+               /* Restore the original values before restarting */
+               *p = old;
                return restart_syscall();
+       }
 
        if (p == &net->ipv6.devconf_all->disable_ipv6) {
                __s32 newf = net->ipv6.devconf_all->disable_ipv6;
@@ -4095,12 +4104,15 @@ int addrconf_sysctl_disable(ctl_table *ctl, int write,
 {
        int *valp = ctl->data;
        int val = *valp;
+       loff_t pos = *ppos;
        int ret;
 
        ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
 
        if (write)
                ret = addrconf_disable_ipv6(ctl, valp, val);
+       if (ret)
+               *ppos = pos;
        return ret;
 }