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Message-Id: <20190919214746.405086721@linuxfoundation.org>
Date: Fri, 20 Sep 2019 00:03:46 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Sean Tranchetti <stranche@...eaurora.org>,
Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>,
"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 05/56] net: Fix null de-reference of device refcount
From: Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>
[ Upstream commit 10cc514f451a0f239aa34f91bc9dc954a9397840 ]
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@...eaurora.org>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
net/core/dev.c | 2 ++
1 file changed, 2 insertions(+)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6837,6 +6837,8 @@ int register_netdevice(struct net_device
ret = notifier_to_errno(ret);
if (ret) {
rollback_registered(dev);
+ rcu_barrier();
+
dev->reg_state = NETREG_UNREGISTERED;
}
/*
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