ACPI / CPPC: Fix KASAN global out of bounds warning

Default value of pcc_subspace_idx is -1.
Make sure to check pcc_subspace_idx before using the same as array index.
This will avoid following KASAN warnings too.

[   15.113449] ==================================================================
[   15.116983] BUG: KASAN: global-out-of-bounds in cppc_get_perf_caps+0xf3/0x3b0
[   15.116983] Read of size 8 at addr ffffffffb9a5c0d8 by task swapper/0/1
[   15.116983] CPU: 3 PID: 1 Comm: swapper/0 Not tainted 4.15.0-rc2+ #2
[   15.116983] Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.2.8 01/26/2016
[   15.116983] Call Trace:
[   15.116983]  dump_stack+0x7c/0xbb
[   15.116983]  print_address_description+0x1df/0x290
[   15.116983]  kasan_report+0x28a/0x370
[   15.116983]  ? cppc_get_perf_caps+0xf3/0x3b0
[   15.116983]  cppc_get_perf_caps+0xf3/0x3b0
[   15.116983]  ? cpc_read+0x210/0x210
[   15.116983]  ? __rdmsr_on_cpu+0x90/0x90
[   15.116983]  ? rdmsrl_on_cpu+0xa9/0xe0
[   15.116983]  ? rdmsr_on_cpu+0x100/0x100
[   15.116983]  ? wrmsrl_on_cpu+0x9c/0xd0
[   15.116983]  ? wrmsrl_on_cpu+0x9c/0xd0
[   15.116983]  ? wrmsr_on_cpu+0xe0/0xe0
[   15.116983]  __intel_pstate_cpu_init.part.16+0x3a2/0x530
[   15.116983]  ? intel_pstate_init_cpu+0x197/0x390
[   15.116983]  ? show_no_turbo+0xe0/0xe0
[   15.116983]  ? __lockdep_init_map+0xa0/0x290
[   15.116983]  intel_pstate_cpu_init+0x30/0x60
[   15.116983]  cpufreq_online+0x155/0xac0
[   15.116983]  cpufreq_add_dev+0x9b/0xb0
[   15.116983]  subsys_interface_register+0x1ae/0x290
[   15.116983]  ? bus_unregister_notifier+0x40/0x40
[   15.116983]  ? mark_held_locks+0x83/0xb0
[   15.116983]  ? _raw_write_unlock_irqrestore+0x32/0x60
[   15.116983]  ? intel_pstate_setup+0xc/0x104
[   15.116983]  ? intel_pstate_setup+0xc/0x104
[   15.116983]  ? cpufreq_register_driver+0x1ce/0x2b0
[   15.116983]  cpufreq_register_driver+0x1ce/0x2b0
[   15.116983]  ? intel_pstate_setup+0x104/0x104
[   15.116983]  intel_pstate_register_driver+0x3a/0xa0
[   15.116983]  intel_pstate_init+0x3c4/0x434
[   15.116983]  ? intel_pstate_setup+0x104/0x104
[   15.116983]  ? intel_pstate_setup+0x104/0x104
[   15.116983]  do_one_initcall+0x9c/0x206
[   15.116983]  ? parameq+0xa0/0xa0
[   15.116983]  ? initcall_blacklisted+0x150/0x150
[   15.116983]  ? lock_downgrade+0x2c0/0x2c0
[   15.116983]  kernel_init_freeable+0x327/0x3f0
[   15.116983]  ? start_kernel+0x612/0x612
[   15.116983]  ? _raw_spin_unlock_irq+0x29/0x40
[   15.116983]  ? finish_task_switch+0xdd/0x320
[   15.116983]  ? finish_task_switch+0x8e/0x320
[   15.116983]  ? rest_init+0xd0/0xd0
[   15.116983]  kernel_init+0xf/0x11a
[   15.116983]  ? rest_init+0xd0/0xd0
[   15.116983]  ret_from_fork+0x24/0x30

[   15.116983] The buggy address belongs to the variable:
[   15.116983]  __key.36299+0x38/0x40

[   15.116983] Memory state around the buggy address:
[   15.116983]  ffffffffb9a5bf80: fa fa fa fa 00 fa fa fa fa fa fa fa 00 fa fa fa
[   15.116983]  ffffffffb9a5c000: fa fa fa fa 00 fa fa fa fa fa fa fa 00 fa fa fa
[   15.116983] >ffffffffb9a5c080: fa fa fa fa 00 fa fa fa fa fa fa fa 00 00 00 00
[   15.116983]                                                     ^
[   15.116983]  ffffffffb9a5c100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   15.116983]  ffffffffb9a5c180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   15.116983] ==================================================================

Fixes: 85b1407b (ACPI / CPPC: Make CPPC ACPI driver aware of PCC subspace IDs)
Reported-by: Changbin Du <changbin.du@intel.com>
Signed-off-by: George Cherian <george.cherian@cavium.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/cppc_acpi.c

@@ -949,7 +949,7 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 	}
 
 	*val = 0;
-	if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM)
+	if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0)
 		vaddr = GET_PCC_VADDR(reg->address, pcc_ss_id);
 	else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
 		vaddr = reg_res->sys_mem_vaddr;
@@ -988,7 +988,7 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
 
-	if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM)
+	if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0)
 		vaddr = GET_PCC_VADDR(reg->address, pcc_ss_id);
 	else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
 		vaddr = reg_res->sys_mem_vaddr;
@@ -1035,14 +1035,15 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
 		*lowest_non_linear_reg, *nominal_reg;
 	u64 high, low, nom, min_nonlinear;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum);
-	struct cppc_pcc_data *pcc_ss_data = pcc_data[pcc_ss_id];
+	struct cppc_pcc_data *pcc_ss_data;
 	int ret = 0, regs_in_pcc = 0;
 
-	if (!cpc_desc) {
+	if (!cpc_desc || pcc_ss_id < 0) {
 		pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
 		return -ENODEV;
 	}
 
+	pcc_ss_data = pcc_data[pcc_ss_id];
 	highest_reg = &cpc_desc->cpc_regs[HIGHEST_PERF];
 	lowest_reg = &cpc_desc->cpc_regs[LOWEST_PERF];
 	lowest_non_linear_reg = &cpc_desc->cpc_regs[LOW_NON_LINEAR_PERF];
@@ -1095,15 +1096,16 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
 	struct cpc_register_resource *delivered_reg, *reference_reg,
 		*ref_perf_reg, *ctr_wrap_reg;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum);
-	struct cppc_pcc_data *pcc_ss_data = pcc_data[pcc_ss_id];
+	struct cppc_pcc_data *pcc_ss_data;
 	u64 delivered, reference, ref_perf, ctr_wrap_time;
 	int ret = 0, regs_in_pcc = 0;
 
-	if (!cpc_desc) {
+	if (!cpc_desc || pcc_ss_id < 0) {
 		pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
 		return -ENODEV;
 	}
 
+	pcc_ss_data = pcc_data[pcc_ss_id];
 	delivered_reg = &cpc_desc->cpc_regs[DELIVERED_CTR];
 	reference_reg = &cpc_desc->cpc_regs[REFERENCE_CTR];
 	ref_perf_reg = &cpc_desc->cpc_regs[REFERENCE_PERF];
@@ -1172,11 +1174,12 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
 	struct cppc_pcc_data *pcc_ss_data = pcc_data[pcc_ss_id];
 	int ret = 0;
 
-	if (!cpc_desc) {
+	if (!cpc_desc || pcc_ss_id < 0) {
 		pr_debug("No CPC descriptor for CPU:%d\n", cpu);
 		return -ENODEV;
 	}
 
+	pcc_ss_data = pcc_data[pcc_ss_id];
 	desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
 
 	/*
@@ -1301,7 +1304,7 @@ unsigned int cppc_get_transition_latency(int cpu_num)
 	struct cpc_desc *cpc_desc;
 	struct cpc_register_resource *desired_reg;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu_num);
-	struct cppc_pcc_data *pcc_ss_data = pcc_data[pcc_ss_id];
+	struct cppc_pcc_data *pcc_ss_data;
 
 	cpc_desc = per_cpu(cpc_desc_ptr, cpu_num);
 	if (!cpc_desc)
@@ -1311,6 +1314,10 @@ unsigned int cppc_get_transition_latency(int cpu_num)
 	if (!CPC_IN_PCC(desired_reg))
 		return CPUFREQ_ETERNAL;
 
+	if (pcc_ss_id < 0)
+		return CPUFREQ_ETERNAL;
+
+	pcc_ss_data = pcc_data[pcc_ss_id];
 	if (pcc_ss_data->pcc_mpar)
 		latency_ns = 60 * (1000 * 1000 * 1000 / pcc_ss_data->pcc_mpar);