| Message ID | 1568145777-29480-1-git-send-email-subashab@codeaurora.org |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] net: Fix null de-reference of device refcount | expand |
From: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org> Date: Tue, 10 Sep 2019 14:02:57 -0600 > In event of failure during register_netdevice, free_netdev is > invoked immediately. free_netdev assumes that all the netdevice > refcounts have been dropped prior to it being called and as a > result frees and clears out the refcount pointer. > > However, this is not necessarily true as some of the operations > in the NETDEV_UNREGISTER notifier handlers queue RCU callbacks for > invocation after a grace period. The IPv4 callback in_dev_rcu_put > tries to access the refcount after free_netdev is called which > leads to a null de-reference- ... > Fix this by waiting for the completion of the call_rcu() in > case of register_netdevice errors. > > Fixes: 93ee31f14f6f ("[NET]: Fix free_netdev on register_netdev failure.") > Cc: Sean Tranchetti <stranche@codeaurora.org> > Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org> Applied and queued up for -stable.
diff --git a/net/core/dev.c b/net/core/dev.c index 49589ed..c7463c9 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -8796,6 +8796,8 @@ int register_netdevice(struct net_device *dev) ret = notifier_to_errno(ret); if (ret) { rollback_registered(dev); + rcu_barrier(); + dev->reg_state = NETREG_UNREGISTERED; } /*
In event of failure during register_netdevice, free_netdev is invoked immediately. free_netdev assumes that all the netdevice refcounts have been dropped prior to it being called and as a result frees and clears out the refcount pointer. However, this is not necessarily true as some of the operations in the NETDEV_UNREGISTER notifier handlers queue RCU callbacks for invocation after a grace period. The IPv4 callback in_dev_rcu_put tries to access the refcount after free_netdev is called which leads to a null de-reference- 44837.761523: <6> Unable to handle kernel paging request at virtual address 0000004a88287000 44837.761651: <2> pc : in_dev_finish_destroy+0x4c/0xc8 44837.761654: <2> lr : in_dev_finish_destroy+0x2c/0xc8 44837.762393: <2> Call trace: 44837.762398: <2> in_dev_finish_destroy+0x4c/0xc8 44837.762404: <2> in_dev_rcu_put+0x24/0x30 44837.762412: <2> rcu_nocb_kthread+0x43c/0x468 44837.762418: <2> kthread+0x118/0x128 44837.762424: <2> ret_from_fork+0x10/0x1c Fix this by waiting for the completion of the call_rcu() in case of register_netdevice errors. Fixes: 93ee31f14f6f ("[NET]: Fix free_netdev on register_netdev failure.") Cc: Sean Tranchetti <stranche@codeaurora.org> Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org> --- net/core/dev.c | 2 ++ 1 file changed, 2 insertions(+)