In the Linux kernel, the following vulnerability has been resolved: drm/msm/gpu: Fix crash when throttling GPU immediately during boot There is a small chance that the GPU is already hot during boot. In that case, the call to of_devfreq_cooling_register() will immediately try to apply devfreq cooling, as seen in the following crash: Unable to handle kernel paging request at virtual address 0000000000014110 pc : a6xx_gpu_busy+0x1c/0x58 [msm] lr : msm_devfreq_get_dev_status+0xbc/0x140 [msm] Call trace: a6xx_gpu_busy+0x1c/0x58 [msm] (P) devfreq_simple_ondemand_func+0x3c/0x150 devfreq_update_target+0x44/0xd8 qos_max_notifier_call+0x30/0x84 blocking_notifier_call_chain+0x6c/0xa0 pm_qos_update_target+0xd0/0x110 freq_qos_apply+0x3c/0x74 apply_constraint+0x88/0x148 __dev_pm_qos_update_request+0x7c/0xcc dev_pm_qos_update_request+0x38/0x5c devfreq_cooling_set_cur_state+0x98/0xf0 __thermal_cdev_update+0x64/0xb4 thermal_cdev_update+0x4c/0x58 step_wise_manage+0x1f0/0x318 __thermal_zone_device_update+0x278/0x424 __thermal_cooling_device_register+0x2bc/0x308 thermal_of_cooling_device_register+0x10/0x1c of_devfreq_cooling_register_power+0x240/0x2bc of_devfreq_cooling_register+0x14/0x20 msm_devfreq_init+0xc4/0x1a0 [msm] msm_gpu_init+0x304/0x574 [msm] adreno_gpu_init+0x1c4/0x2e0 [msm] a6xx_gpu_init+0x5c8/0x9c8 [msm] adreno_bind+0x2a8/0x33c [msm] ... At this point we haven't initialized the GMU at all yet, so we cannot read the GMU registers inside a6xx_gpu_busy(). A similar issue was fixed before in commit 6694482a70e9 ("drm/msm: Avoid unclocked GMU register access in 6xx gpu_busy"): msm_devfreq_init() does call devfreq_suspend_device(), but unlike msm_devfreq_suspend(), it doesn't set the df->suspended flag accordingly. This means the df->suspended flag does not match the actual devfreq state after initialization and msm_devfreq_get_dev_status() will end up accessing GMU registers, causing the crash. Fix this by setting df->suspended correctly during initialization. Patchwork: https://patchwork.freedesktop.org/patch/650772/
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