From: Oliver O'Halloran <oohall@gmail.com> commit d0a72efac89d1c35ac55197895201b7b94c5e6ef upstream. The cpufreq driver has a use-after-free that we can hit if: a) There's an OCC message pending when the notifier is registered, and b) The cpufreq driver fails to register with the core. When a) occurs the notifier schedules a workqueue item to handle the message. The backing work_struct is located on chips[].throttle and when b) happens we clean up by freeing the array. Once we get to the (now free) queued item and the kernel crashes. Fixes: c5e29ea7ac14 ("cpufreq: powernv: Fix bugs in powernv_cpufreq_{init/exit}") Cc: stable@vger.kernel.org # v4.6+ Signed-off-by: Oliver O'Halloran <oohall@gmail.com> Reviewed-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200206062622.28235-1-oohall@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/cpufreq/powernv-cpufreq.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c index 5fff39d..687c92e 100644 --- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -1081,6 +1081,12 @@ static int init_chip_info(void) static inline void clean_chip_info(void) { + int i; + + /* flush any pending work items */ + if (chips) + for (i = 0; i < nr_chips; i++) + cancel_work_sync(&chips[i].throttle); kfree(chips); } -- 1.8.3