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.
Cc: Vaidyanathan Srinivasan <sva...@linux.vnet.ibm.com>
Fixes: c5e29ea ("cpufreq: powernv: Fix bugs in powernv_cpufreq_{init/exit}")
Signed-off-by: Oliver O'Halloran <ooh...@gmail.com>
---
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 56f4bc0..1806b1d 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -1080,6 +1080,12 @@ 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);
}
--
2.9.5
