ide: serverworks: potential overflow in svwks_set_pio_mode()

The "drive->dn" variable is a u8 controlled by root.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ide/serverworks.c

@@ -115,6 +115,9 @@ static void svwks_set_pio_mode(ide_hwif_t *hwif, ide_drive_t *drive)
 	struct pci_dev *dev = to_pci_dev(hwif->dev);
 	const u8 pio = drive->pio_mode - XFER_PIO_0;
 
+	if (drive->dn >= ARRAY_SIZE(drive_pci))
+		return;
+
 	pci_write_config_byte(dev, drive_pci[drive->dn], pio_modes[pio]);
 
 	if (svwks_csb_check(dev)) {
@@ -141,6 +144,9 @@ static void svwks_set_dma_mode(ide_hwif_t *hwif, ide_drive_t *drive)
 
 	u8 ultra_enable	 = 0, ultra_timing = 0, dma_timing = 0;
 
+	if (drive->dn >= ARRAY_SIZE(drive_pci2))
+		return;
+
 	pci_read_config_byte(dev, (0x56|hwif->channel), &ultra_timing);
 	pci_read_config_byte(dev, 0x54, &ultra_enable);