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2bce1ebed1
When a macsec interface is created, it increases a refcnt to a lower
device(real device). when macsec interface is deleted, the refcnt is
decreased in macsec_free_netdev(), which is ->priv_destructor() of
macsec interface.
The problem scenario is this.
When nested macsec interfaces are exiting, the exit routine of the
macsec module makes refcnt leaks.
Test commands:
ip link add dummy0 type dummy
ip link add macsec0 link dummy0 type macsec
ip link add macsec1 link macsec0 type macsec
modprobe -rv macsec
[ 208.629433] unregister_netdevice: waiting for macsec0 to become free. Usage count = 1
Steps of exit routine of macsec module are below.
1. Calls ->dellink() in __rtnl_link_unregister().
2. Checks refcnt and wait refcnt to be 0 if refcnt is not 0 in
netdev_run_todo().
3. Calls ->priv_destruvtor() in netdev_run_todo().
Step2 checks refcnt, but step3 decreases refcnt.
So, step2 waits forever.
This patch makes the macsec module do not hold a refcnt of the lower
device because it already holds a refcnt of the lower device with
netdev_upper_dev_link().
Fixes: c09440f7dc ("macsec: introduce IEEE 802.1AE driver")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
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.