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cpufreq: powernv: Fix use-after-free

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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: c5e29ea7ac ("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
This commit is contained in:
Oliver O'Halloran 2020-02-06 17:26:21 +11:00 committed by Michael Ellerman
parent ffd3eaf178
commit d0a72efac8
1 changed files with 6 additions and 0 deletions
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6
drivers/cpufreq/powernv-cpufreq.c
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@ -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);
}