radeon: Do not directly dereference pointers to BIOS area.

commit f2c9e560 upstream.

Use readb() and memcpy_fromio() accessors instead.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/radeon/radeon_bios.c

@@ -76,7 +76,7 @@ static bool igp_read_bios_from_vram(struct radeon_device *rdev)
 
 static bool radeon_read_bios(struct radeon_device *rdev)
 {
-	uint8_t __iomem *bios;
+	uint8_t __iomem *bios, val1, val2;
 	size_t size;
 
 	rdev->bios = NULL;
@@ -86,15 +86,19 @@ static bool radeon_read_bios(struct radeon_device *rdev)
 		return false;
 	}
 
-	if (size == 0 || bios[0] != 0x55 || bios[1] != 0xaa) {
+	val1 = readb(&bios[0]);
+	val2 = readb(&bios[1]);
+
+	if (size == 0 || val1 != 0x55 || val2 != 0xaa) {
 		pci_unmap_rom(rdev->pdev, bios);
 		return false;
 	}
-	rdev->bios = kmemdup(bios, size, GFP_KERNEL);
+	rdev->bios = kzalloc(size, GFP_KERNEL);
 	if (rdev->bios == NULL) {
 		pci_unmap_rom(rdev->pdev, bios);
 		return false;
 	}
+	memcpy_fromio(rdev->bios, bios, size);
 	pci_unmap_rom(rdev->pdev, bios);
 	return true;
 }