From aca51397d01474f80cab8fc978559b45f2e453ad Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Thu, 8 May 2008 01:24:25 -0700 Subject: [PATCH] netns: Fix arbitrary net_device-s corruptions on net_ns stop. When a net namespace is destroyed, some devices (those, not killed on ns stop explicitly) are moved back to init_net. The problem, is that this net_ns change has one point of failure - the __dev_alloc_name() may be called if a name collision occurs (and this is easy to trigger). This allocator performs a likely-to-fail GFP_ATOMIC allocation to find a suitable number. Other possible conditions that may cause error (for device being ns local or not registered) are always false in this case. So, when this call fails, the device is unregistered. But this is *not* the right thing to do, since after this the device may be released (and kfree-ed) improperly. E. g. bridges require more actions (sysfs update, timer disarming, etc.), some other devices want to remove their private areas from lists, etc. I. e. arbitrary use-after-free cases may occur. The proposed fix is the following: since the only reason for the dev_change_net_namespace to fail is the name generation, we may give it a unique fall-back name w/o %d-s in it - the dev one, since ifindexes are still unique. So make this change, raise the failure-case printk loglevel to EMERG and replace the unregister_netdevice call with BUG(). [ Use snprintf() -DaveM ] Signed-off-by: Pavel Emelyanov Signed-off-by: David S. Miller --- net/core/dev.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index d334446a8e..4addaf0df9 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4480,17 +4480,19 @@ static void __net_exit default_device_exit(struct net *net) rtnl_lock(); for_each_netdev_safe(net, dev, next) { int err; + char fb_name[IFNAMSIZ]; /* Ignore unmoveable devices (i.e. loopback) */ if (dev->features & NETIF_F_NETNS_LOCAL) continue; /* Push remaing network devices to init_net */ - err = dev_change_net_namespace(dev, &init_net, "dev%d"); + snprintf(fb_name, IFNAMSIZ, "dev%d", dev->ifindex); + err = dev_change_net_namespace(dev, &init_net, fb_name); if (err) { - printk(KERN_WARNING "%s: failed to move %s to init_net: %d\n", + printk(KERN_EMERG "%s: failed to move %s to init_net: %d\n", __func__, dev->name, err); - unregister_netdevice(dev); + BUG(); } } rtnl_unlock(); -- 2.39.5