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(+)
--- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -1080,6 +1080,12 @@ free_and_return:
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); }