Re: [PATCH net/ipv6] net/ipv6: avoid possible dead locking on addr_gen_mode sysctl

[David Miller]

From: Felix Jia 
Date: Mon, 27 Feb 2017 12:41:23 +1300

> The addr_gen_mode variable can be accessed by both sysctl and netlink.
> Repleacd rtnl_lock() with rtnl_trylock() protect the sysctl operation to
> avoid the possbile dead lock.`
> 
> Signed-off-by: Felix Jia 

Applied and queued up for -stable, thanks.

[PATCH net/ipv6] net/ipv6: avoid possible dead locking on addr_gen_mode sysctl

[Felix Jia]

The addr_gen_mode variable can be accessed by both sysctl and netlink.
Repleacd rtnl_lock() with rtnl_trylock() protect the sysctl operation to
avoid the possbile dead lock.`

Signed-off-by: Felix Jia 
---
 net/ipv6/addrconf.c | 22 +++---
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 3a2025f5bf2c..cfc485a8e1c0 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5692,13 +5692,18 @@ static int addrconf_sysctl_addr_gen_mode(struct 
ctl_table *ctl, int write,
struct inet6_dev *idev = (struct inet6_dev *)ctl->extra1;
struct net *net = (struct net *)ctl->extra2;
 
+   if (!rtnl_trylock())
+   return restart_syscall();
+
ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
 
if (write) {
new_val = *((int *)ctl->data);
 
-   if (check_addr_gen_mode(new_val) < 0)
-   return -EINVAL;
+   if (check_addr_gen_mode(new_val) < 0) {
+   ret = -EINVAL;
+   goto out;
+   }
 
/* request for default */
if (>ipv6.devconf_dflt->addr_gen_mode == ctl->data) {
@@ -5707,20 +5712,23 @@ static int addrconf_sysctl_addr_gen_mode(struct 
ctl_table *ctl, int write,
/* request for individual net device */
} else {
if (!idev)
-   return ret;
+   goto out;
 
-   if (check_stable_privacy(idev, net, new_val) < 0)
-   return -EINVAL;
+   if (check_stable_privacy(idev, net, new_val) < 0) {
+   ret = -EINVAL;
+   goto out;
+   }
 
if (idev->cnf.addr_gen_mode != new_val) {
idev->cnf.addr_gen_mode = new_val;
-   rtnl_lock();
addrconf_dev_config(idev->dev);
-   rtnl_unlock();
}
}
}
 
+out:
+   rtnl_unlock();
+
return ret;
 }
 
-- 
2.11.0