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The function hfcpci_softirq() is a timer handler. If it
is running, the timer_pending() will return 0 and the
del_timer_sync() in HFC_cleanup() will not be executed.
As a result, the use-after-free bug will happen. The
process is shown below:
(cleanup routine) | (timer handler)
HFC_cleanup() | hfcpci_softirq()
if (timer_pending(&hfc_tl)) |
del_timer_sync() |
... | ...
pci_unregister_driver(hc) |
driver_unregister | driver_for_each_device
bus_remove_driver | _hfcpci_softirq
driver_detach | ...
put_device(dev) //[1]FREE |
| dev_get_drvdata(dev) //[2]USE
The device is deallocated is position [1] and used in
position [2].
Fix by removing the "timer_pending" check in HFC_cleanup(),
which makes sure that the hfcpci_softirq() have finished
before the resource is deallocated.
Fixes: 009fc857c5 ("mISDN: fix possible use-after-free in HFC_cleanup()")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
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.