drm/radeon: Avoid NULL pointer dereference from atom_index_iio() allocation failure

Smatch anlysis:

drivers/gpu/drm/radeon/atom.c:1242 atom_index_iio() error: potential null
 dereference 'ctx->iio'.  (kzalloc returns null)

Also cleaned up some checks before calls to kfree(). kfree(NULL) is OK.

Cc: David Airlie <airlied@linux.ie>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Michel Dänzer" <michel.daenzer@amd.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: NTim Gardner <tim.gardner@canonical.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/atom.c

@@ -1238,6 +1238,8 @@ static int atom_iio_len[] = { 1, 2, 3, 3, 3, 3, 4, 4, 4, 3 };
 static void atom_index_iio(struct atom_context *ctx, int base)
 {
 	ctx->iio = kzalloc(2 * 256, GFP_KERNEL);
+	if (!ctx->iio)
+		return;
 	while (CU8(base) == ATOM_IIO_START) {
 		ctx->iio[CU8(base + 1)] = base + 2;
 		base += 2;
@@ -1287,6 +1289,10 @@ struct atom_context *atom_parse(struct card_info *card, void *bios)
 	ctx->cmd_table = CU16(base + ATOM_ROM_CMD_PTR);
 	ctx->data_table = CU16(base + ATOM_ROM_DATA_PTR);
 	atom_index_iio(ctx, CU16(ctx->data_table + ATOM_DATA_IIO_PTR) + 4);
+	if (!ctx->iio) {
+		atom_destroy(ctx);
+		return NULL;
+	}
 
 	str = CSTR(CU16(base + ATOM_ROM_MSG_PTR));
 	while (*str && ((*str == '\n') || (*str == '\r')))
@@ -1335,7 +1341,6 @@ int atom_asic_init(struct atom_context *ctx)
 
 void atom_destroy(struct atom_context *ctx)
 {
-	if (ctx->iio)
 	kfree(ctx->iio);
 	kfree(ctx);
 }

drivers/gpu/drm/radeon/radeon_device.c

@@ -758,6 +758,11 @@ int radeon_atombios_init(struct radeon_device *rdev)
 	atom_card_info->pll_write = cail_pll_write;
 
 	rdev->mode_info.atom_context = atom_parse(atom_card_info, rdev->bios);
+	if (!rdev->mode_info.atom_context) {
+		radeon_atombios_fini(rdev);
+		return -ENOMEM;
+	}
+
 	mutex_init(&rdev->mode_info.atom_context->mutex);
 	radeon_atom_initialize_bios_scratch_regs(rdev->ddev);
 	atom_allocate_fb_scratch(rdev->mode_info.atom_context);
@@ -777,9 +782,11 @@ void radeon_atombios_fini(struct radeon_device *rdev)
 {
 	if (rdev->mode_info.atom_context) {
 		kfree(rdev->mode_info.atom_context->scratch);
-		kfree(rdev->mode_info.atom_context);
 	}
+	kfree(rdev->mode_info.atom_context);
+	rdev->mode_info.atom_context = NULL;
 	kfree(rdev->mode_info.atom_card_info);
+	rdev->mode_info.atom_card_info = NULL;
 }
 
 /* COMBIOS */