From 9753c0ab89b7516aba4884dc3cc725ca33c2e3da Mon Sep 17 00:00:00 2001 From: Christian Loehle Date: Wed, 22 Jul 2026 10:38:25 +0100 Subject: [PATCH] cpufreq: cppc: Sanitize lockless policy limit snapshots cppc_cpufreq_update_perf_limits() reads policy->min and policy->max without holding the policy lock. The cpufreq core updates those fields with separate stores, so a reader can observe the old minimum together with the new maximum and construct MIN_PERF greater than MAX_PERF. Read both fields once and, if the lockless snapshot is inconsistent, reduce the minimum to the observed maximum. This matches the conservative correction used by cpufreq_driver_resolve_freq() and ensures that CPPC never receives an inverted limit pair. Fixes: ea3db45ae476 ("cpufreq: cppc: Update MIN_PERF/MAX_PERF in target callbacks") Cc: stable@vger.kernel.org Signed-off-by: Christian Loehle Link: https://patch.msgid.link/20260722093825.1030594-3-christian.loehle@arm.com Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/cppc_cpufreq.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index b943bf78d3f5..6fe0e972952a 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -290,19 +290,32 @@ static inline void cppc_freq_invariance_exit(void) } #endif /* CONFIG_ACPI_CPPC_CPUFREQ_FIE */ +static void cppc_cpufreq_get_perf_limits(struct cppc_cpudata *cpu_data, + struct cpufreq_policy *policy, + u32 *min_perf, u32 *max_perf) +{ + struct cppc_perf_caps *caps = &cpu_data->perf_caps; + unsigned int min_freq, max_freq; + u32 min, max; + + min_freq = READ_ONCE(policy->min); + max_freq = READ_ONCE(policy->max); + if (unlikely(min_freq > max_freq)) + min_freq = max_freq; + + min = cppc_khz_to_perf(caps, min_freq); + max = cppc_khz_to_perf(caps, max_freq); + + *min_perf = clamp_t(u32, min, caps->lowest_perf, caps->highest_perf); + *max_perf = clamp_t(u32, max, caps->lowest_perf, caps->highest_perf); +} + static void cppc_cpufreq_update_perf_limits(struct cppc_cpudata *cpu_data, struct cpufreq_policy *policy) { - struct cppc_perf_caps *caps = &cpu_data->perf_caps; - u32 min_perf, max_perf; - - min_perf = cppc_khz_to_perf(caps, policy->min); - max_perf = cppc_khz_to_perf(caps, policy->max); - - cpu_data->perf_ctrls.min_perf = - clamp_t(u32, min_perf, caps->lowest_perf, caps->highest_perf); - cpu_data->perf_ctrls.max_perf = - clamp_t(u32, max_perf, caps->lowest_perf, caps->highest_perf); + cppc_cpufreq_get_perf_limits(cpu_data, policy, + &cpu_data->perf_ctrls.min_perf, + &cpu_data->perf_ctrls.max_perf); } static int cppc_cpufreq_set_target(struct cpufreq_policy *policy,