| Message ID | 20211126015942.2918542-1-william.xuanziyang@huawei.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 01d9cc2dea3fde3bad6d27f464eff463496e2b00 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] net: vlan: fix underflow for the real_dev refcnt | expand |
Hello: This patch was applied to netdev/net.git (master) by Jakub Kicinski <kuba@kernel.org>: On Fri, 26 Nov 2021 09:59:42 +0800 you wrote: > Inject error before dev_hold(real_dev) in register_vlan_dev(), > and execute the following testcase: > > ip link add dev dummy1 type dummy > ip link add name dummy1.100 link dummy1 type vlan id 100 > ip link del dev dummy1 > > [...] Here is the summary with links: - [net] net: vlan: fix underflow for the real_dev refcnt https://git.kernel.org/netdev/net/c/01d9cc2dea3f You are awesome, thank you!
diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c index a3a0a5e994f5..abaa5d96ded2 100644 --- a/net/8021q/vlan.c +++ b/net/8021q/vlan.c @@ -184,9 +184,6 @@ int register_vlan_dev(struct net_device *dev, struct netlink_ext_ack *extack) if (err) goto out_unregister_netdev; - /* Account for reference in struct vlan_dev_priv */ - dev_hold(real_dev); - vlan_stacked_transfer_operstate(real_dev, dev, vlan); linkwatch_fire_event(dev); /* _MUST_ call rfc2863_policy() */ diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c index ab6dee28536d..a54535cbcf4c 100644 --- a/net/8021q/vlan_dev.c +++ b/net/8021q/vlan_dev.c @@ -615,6 +615,9 @@ static int vlan_dev_init(struct net_device *dev) if (!vlan->vlan_pcpu_stats) return -ENOMEM; + /* Get vlan's reference to real_dev */ + dev_hold(real_dev); + return 0; }
Inject error before dev_hold(real_dev) in register_vlan_dev(), and execute the following testcase: ip link add dev dummy1 type dummy ip link add name dummy1.100 link dummy1 type vlan id 100 ip link del dev dummy1 When the dummy netdevice is removed, we will get a WARNING as following: ======================================================================= refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 2 PID: 0 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0 and an endless loop of: ======================================================================= unregister_netdevice: waiting for dummy1 to become free. Usage count = -1073741824 That is because dev_put(real_dev) in vlan_dev_free() be called without dev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev underflow. Move the dev_hold(real_dev) to vlan_dev_init() which is the call-back of ndo_init(). That makes dev_hold() and dev_put() for vlan's real_dev symmetrical. Fixes: 563bcbae3ba2 ("net: vlan: fix a UAF in vlan_dev_real_dev()") Reported-by: Petr Machata <petrm@nvidia.com> Suggested-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com> --- net/8021q/vlan.c | 3 --- net/8021q/vlan_dev.c | 3 +++ 2 files changed, 3 insertions(+), 3 deletions(-)