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H A D | cpufreq.c | diff e6e8df07268c1f75dd9215536e2ce4587b70f977 Wed Nov 06 23:08:17 CST 2019 Kai Shen <shenkai8@huawei.com> cpufreq: Add NULL checks to show() and store() methods of cpufreq
Add NULL checks to show() and store() in cpufreq.c to avoid attempts to invoke a NULL callback.
Though some interfaces of cpufreq are set as read-only, users can still get write permission using chmod which can lead to a kernel crash, as follows:
chmod +w /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq echo 1 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
This bug was found in linux 4.19.
Signed-off-by: Kai Shen <shenkai8@huawei.com> Reported-by: Feilong Lin <linfeilong@huawei.com> Reviewed-by: Feilong Lin <linfeilong@huawei.com> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> [ rjw: Subject & changelog ] Cc: All applicable <stable@vger.kernel.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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