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[2/2] arch_topology: Sanity check cpumask in thermal pressure update

Message ID 20220118185612.2067031-2-bjorn.andersson@linaro.org
State New
Headers show
Series None | expand

Commit Message

Bjorn Andersson Jan. 18, 2022, 6:56 p.m. UTC
Occasionally during boot the Qualcomm cpufreq driver was able to cause
an invalid memory access in topology_update_thermal_pressure() on the

	if (max_freq <= capped_freq)

It turns out that this was caused by a race, which resulted in the
cpumask passed to the function being empty, in which case
cpumask_first() will return a cpu beyond the number of valid cpus, which
when used to access the per_cpu max_freq would return invalid pointer.

The bug in the Qualcomm cpufreq driver is being fixed, but having a
sanity check of the arguments would have saved quite a bit of time and
it's not unlikely that others will run into the same issue.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
 drivers/base/arch_topology.c | 3 +++
 1 file changed, 3 insertions(+)
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diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 976154140f0b..6560a0c3b969 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -177,6 +177,9 @@  void topology_update_thermal_pressure(const struct cpumask *cpus,
 	u32 max_freq;
 	int cpu;
+	if (WARN_ON(cpumask_empty(cpus)))
+		return;
 	cpu = cpumask_first(cpus);
 	max_capacity = arch_scale_cpu_capacity(cpu);
 	max_freq = per_cpu(freq_factor, cpu);