[net] net: Fix null de-reference of device refcount
diff mbox series

Message ID 1568145777-29480-1-git-send-email-subashab@codeaurora.org
State Accepted
Delegated to: David Miller
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Series
  • [net] net: Fix null de-reference of device refcount
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Commit Message

Subash Abhinov Kasiviswanathan Sept. 10, 2019, 8:02 p.m. UTC
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(+)

Comments

David Miller Sept. 12, 2019, 10:56 a.m. UTC | #1
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.

Patch
diff mbox series

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;
 	}
 	/*