CVE-2021-47187 Information

Description

In the Linux kernel the following vulnerability has been resolved:

arm64: dts: qcom: msm8998: Fix CPU/L2 idle state latency and residency

The entry/exit latency and minimum residency in state for the idle states of MSM8998 were ..bad: first of all for all of them the timings were written for CPU sleep but the min-residency-us param was miscalculated (supposedly while porting this from downstream); Then the power collapse states are setting PC on both the CPU cluster and the L2 cache which have different timings: in the specific case of L2 the times are higher so these ones should be taken into account instead of the CPU ones.

This parameter misconfiguration was not giving particular issues because on MSM8998 there was no CPU scaling at all so cluster/L2 power collapse was rarely (if ever) hit. When CPU scaling is enabled though the wrong timings will produce SoC unstability shown to the user as random apparently error-less sudden reboots and/or lockups.

This set of parameters are stabilizing the SoC when CPU scaling is ON and when power collapse is frequently hit.

Reference

https://git.kernel.org/stable/c/a14d7038ea201c5526375becfc43b9ba281b1e82 https://git.kernel.org/stable/c/e52fecdd0c142b95c720683885b06ee3f0e065c8 https://git.kernel.org/stable/c/118c826ef8b43efe0fda8faf419673707ee8c5e5 https://git.kernel.org/stable/c/3f1dcaff642e75c1d2ad03f783fa8a3b1f56dd50