Commit 15eece6c authored by Yunhui Cui's avatar Yunhui Cui Committed by Rafael J. Wysocki
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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] [<ffffffff809a5818>] cppc_allow_fast_switch+0x6a/0xd4
...
Kernel panic - not syncing: Attempted to kill init!

Fixes: 3cc30dd0 ("cpufreq: CPPC: Enable fast_switch")
Reported-by: default avatarXu Lu <luxu.kernel@bytedance.com>
Signed-off-by: default avatarYunhui Cui <cuiyunhui@bytedance.com>
Link: https://patch.msgid.link/20250604023036.99553-1-cuiyunhui@bytedance.com


[ rjw: New subject ]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 19272b37

drivers/acpi/cppc_acpi.c

+1 −1
Original line number Diff line number Diff line
@@ -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) &&