drm/radeon/kms/atom: fix gpio i2c table overrun (v2)

The GPIO_I2C_INFO table does not always have
ATOM_MAX_SUPPORTED_DEVICE entries. Limit
the number of indices to the size of the
table.

Should fix Novell bug 589022.

v2: fix typo
Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: Stable <stable@kernel.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_atombios.c

@@ -69,16 +69,19 @@ static inline struct radeon_i2c_bus_rec radeon_lookup_i2c_gpio(struct radeon_dev
 	struct radeon_i2c_bus_rec i2c;
 	int index = GetIndexIntoMasterTable(DATA, GPIO_I2C_Info);
 	struct _ATOM_GPIO_I2C_INFO *i2c_info;
-	uint16_t data_offset;
-	int i;
+	uint16_t data_offset, size;
+	int i, num_indices;
 
 	memset(&i2c, 0, sizeof(struct radeon_i2c_bus_rec));
 	i2c.valid = false;
 
-	if (atom_parse_data_header(ctx, index, NULL, NULL, NULL, &data_offset)) {
+	if (atom_parse_data_header(ctx, index, &size, NULL, NULL, &data_offset)) {
 		i2c_info = (struct _ATOM_GPIO_I2C_INFO *)(ctx->bios + data_offset);
 
-		for (i = 0; i < ATOM_MAX_SUPPORTED_DEVICE; i++) {
+		num_indices = (size - sizeof(ATOM_COMMON_TABLE_HEADER)) /
+			sizeof(ATOM_GPIO_I2C_ASSIGMENT);
+
+		for (i = 0; i < num_indices; i++) {
 			gpio = &i2c_info->asGPIO_Info[i];
 
 			if (gpio->sucI2cId.ucAccess == id) {