From 15eece6c5b05e5f9db0711978c3e3b7f1a2cfe12 Mon Sep 17 00:00:00 2001 From: Yunhui Cui Date: Wed, 4 Jun 2025 10:30:36 +0800 Subject: [PATCH] ACPI: CPPC: Fix NULL pointer dereference when nosmp is used With nosmp in cmdline, other CPUs are not brought up, leaving their cpc_desc_ptr NULL. CPU0's iteration via for_each_possible_cpu() dereferences these NULL pointers, causing panic. Panic backtrace: [ 0.401123] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000b8 ... [ 0.403255] [] cppc_allow_fast_switch+0x6a/0xd4 ... Kernel panic - not syncing: Attempted to kill init! Fixes: 3cc30dd00a58 ("cpufreq: CPPC: Enable fast_switch") Reported-by: Xu Lu Signed-off-by: Yunhui Cui Link: https://patch.msgid.link/20250604023036.99553-1-cuiyunhui@bytedance.com [ rjw: New subject ] Signed-off-by: Rafael J. Wysocki --- drivers/acpi/cppc_acpi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index a9ae2fd62863..6b649031808f 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -476,7 +476,7 @@ bool cppc_allow_fast_switch(void) struct cpc_desc *cpc_ptr; int cpu; - for_each_possible_cpu(cpu) { + for_each_present_cpu(cpu) { cpc_ptr = per_cpu(cpc_desc_ptr, cpu); desired_reg = &cpc_ptr->cpc_regs[DESIRED_PERF]; if (!CPC_IN_SYSTEM_MEMORY(desired_reg) && -- 2.50.1