4.9-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 2f66196208c98b3d1b4294edffb2c5a8197be899 ]
cpuinfo_cur_freq gets current CPU frequency as detected by hardware while scaling_cur_freq last known CPU frequency. Some platforms may not allow checking the CPU frequency of an offline CPU or the associated resources may have been released via cpufreq_exit when the CPU gets offlined, in which case the policy would have been invalidated already. If we attempt to get current frequency from the hardware, it may result in hang or crash.
For example on Juno, I see:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000188 [0000000000000188] pgd=0000000000000000 Internal error: Oops: 96000004 [#1] PREEMPT SMP Modules linked in: CPU: 5 PID: 4202 Comm: cat Not tainted 4.20.0-08251-ga0f2c0318a15-dirty #87 Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform pstate: 40000005 (nZcv daif -PAN -UAO) pc : scmi_cpufreq_get_rate+0x34/0xb0 lr : scmi_cpufreq_get_rate+0x34/0xb0 Call trace: scmi_cpufreq_get_rate+0x34/0xb0 __cpufreq_get+0x34/0xc0 show_cpuinfo_cur_freq+0x24/0x78 show+0x40/0x60 sysfs_kf_seq_show+0xc0/0x148 kernfs_seq_show+0x44/0x50 seq_read+0xd4/0x480 kernfs_fop_read+0x15c/0x208 __vfs_read+0x60/0x188 vfs_read+0x94/0x150 ksys_read+0x6c/0xd8 __arm64_sys_read+0x24/0x30 el0_svc_common+0x78/0x100 el0_svc_handler+0x38/0x78 el0_svc+0x8/0xc ---[ end trace 3d1024e58f77f6b2 ]---
So fix the issue by checking if the policy is invalid early in __cpufreq_get before attempting to get the current frequency.
Signed-off-by: Sudeep Holla sudeep.holla@arm.com Acked-by: Viresh Kumar viresh.kumar@linaro.org Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com
Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/cpufreq/cpufreq.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index d6d91e8afa9e..61fe4bbc6dc0 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1496,17 +1496,16 @@ static unsigned int __cpufreq_get(struct cpufreq_policy *policy) { unsigned int ret_freq = 0;
- if (!cpufreq_driver->get) + if (unlikely(policy_is_inactive(policy)) || !cpufreq_driver->get) return ret_freq;
ret_freq = cpufreq_driver->get(policy->cpu);
/* - * Updating inactive policies is invalid, so avoid doing that. Also - * if fast frequency switching is used with the given policy, the check + * If fast frequency switching is used with the given policy, the check * against policy->cur is pointless, so skip it in that case too. */ - if (unlikely(policy_is_inactive(policy)) || policy->fast_switch_enabled) + if (policy->fast_switch_enabled) return ret_freq;
if (ret_freq && policy->cur &&