10cc514f45
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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.