PCI: tegra194: Fix possible array out of bounds access

Add check to fix the possible array out of bounds violation by
making speed equal to GEN1_CORE_CLK_FREQ when its value is more
than the size of "pcie_gen_freq" array. This array has size of
four but possible speed (CLS) values are from "0 to 0xF". So,
"speed - 1" values are "-1 to 0xE".
Suggested-by: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
Link: https://lore.kernel.org/lkml/72b9168b-d4d6-4312-32ea-69358df2f2d0@nvidia.com/Acked-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/pci/controller/dwc/pcie-tegra194.c

@@ -223,6 +223,7 @@
 #define EP_STATE_ENABLED	1
 
 static const unsigned int pcie_gen_freq[] = {
+	GEN1_CORE_CLK_FREQ,	/* PCI_EXP_LNKSTA_CLS == 0; undefined */
 	GEN1_CORE_CLK_FREQ,
 	GEN2_CORE_CLK_FREQ,
 	GEN3_CORE_CLK_FREQ,
@@ -459,7 +460,11 @@ static irqreturn_t tegra_pcie_ep_irq_thread(int irq, void *arg)
 
 	speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
 		PCI_EXP_LNKSTA_CLS;
-	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed - 1]);
+
+	if (speed >= ARRAY_SIZE(pcie_gen_freq))
+		speed = 0;
+
+	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed]);
 
 	if (pcie->of_data->has_ltr_req_fix)
 		return IRQ_HANDLED;
@@ -1020,7 +1025,11 @@ static int tegra_pcie_dw_start_link(struct dw_pcie *pci)
 
 	speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
 		PCI_EXP_LNKSTA_CLS;
-	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed - 1]);
+
+	if (speed >= ARRAY_SIZE(pcie_gen_freq))
+		speed = 0;
+
+	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed]);
 
 	tegra_pcie_enable_interrupts(pp);