linux-kernel - [PATCH] ACPI / CPPC: Fix negative array index read in cppc_set

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Date:   Wed, 13 Dec 2017 16:45:41 -0600
From:   "Gustavo A. R. Silva" <garsilva@...eddedor.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        George Cherian <george.cherian@...ium.com>
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>
Subject: [PATCH] ACPI / CPPC: Fix negative array index read in cppc_set_perf

If pcc_ss_id is less than 0, there is a negative array index read
before verifying pcc_ss_id is not a negative value.

Fix this by removing the code that triggers this issue.

Notice that this code is already properly placed after the check
on pcc_ss_id at line 1182: pcc_ss_data = pcc_data[pcc_ss_id];

Addresses-Coverity-ID: 1426090 ("Negative array index read")
Fixes: 1ecbd7170d65 ("ACPI / CPPC: Fix KASAN global out of bounds warning")
Signed-off-by: Gustavo A. R. Silva <garsilva@...eddedor.com>
---
 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 30e84cc..06ea474 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1171,7 +1171,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
 	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
 	struct cpc_register_resource *desired_reg;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
-	struct cppc_pcc_data *pcc_ss_data = pcc_data[pcc_ss_id];
+	struct cppc_pcc_data *pcc_ss_data;
 	int ret = 0;
 
 	if (!cpc_desc || pcc_ss_id < 0) {
-- 
2.7.4