greybus: Avoid fake flexible array for response data

FORTIFY_SOURCE has been ignoring 0-sized destinations while the kernel
code base has been converted to flexible arrays. In order to enforce
the 0-sized destinations (e.g. with __counted_by), the remaining 0-sized
destinations need to be handled. Instead of converting an empty struct
into using a flexible array, just directly use a pointer without any
additional indirection. Remove struct gb_bootrom_get_firmware_response
and struct gb_fw_download_fetch_firmware_response.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20240304211940.it.083-kees@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/greybus/bootrom.c b/drivers/staging/greybus/bootrom.c
index 79581457c4afbc151b86df74aef62466689e7ba2..c0d338db6b525a95ca4e3d6f1b733d67486c6c51 100644 (file)
--- a/drivers/staging/greybus/bootrom.c
+++ b/drivers/staging/greybus/bootrom.c
@@ -243,10 +243,10 @@ static int gb_bootrom_get_firmware(struct gb_operation *op)
        struct gb_bootrom *bootrom = gb_connection_get_data(op->connection);
        const struct firmware *fw;
        struct gb_bootrom_get_firmware_request *firmware_request;
-       struct gb_bootrom_get_firmware_response *firmware_response;
        struct device *dev = &op->connection->bundle->dev;
        unsigned int offset, size;
        enum next_request_type next_request;
+       u8 *firmware_response;
        int ret = 0;
 
        /* Disable timeouts */
@@ -280,15 +280,15 @@ static int gb_bootrom_get_firmware(struct gb_operation *op)
                goto unlock;
        }
 
-       if (!gb_operation_response_alloc(op, sizeof(*firmware_response) + size,
-                                        GFP_KERNEL)) {
+       /* gb_bootrom_get_firmware_response contains only a byte array */
+       if (!gb_operation_response_alloc(op, size, GFP_KERNEL)) {
                dev_err(dev, "%s: error allocating response\n", __func__);
                ret = -ENOMEM;
                goto unlock;
        }
 
        firmware_response = op->response->payload;
-       memcpy(firmware_response->data, fw->data + offset, size);
+       memcpy(firmware_response, fw->data + offset, size);
 
        dev_dbg(dev, "responding with firmware (offs = %u, size = %u)\n",
                offset, size);

diff --git a/drivers/staging/greybus/fw-download.c b/drivers/staging/greybus/fw-download.c
index 2a5c6d1b049c8f6ac83d3e2ac6e130c1ecba6c8c..9a09bd3af79ba0dcf7efa683f4e86246bcd473a5 100644 (file)
--- a/drivers/staging/greybus/fw-download.c
+++ b/drivers/staging/greybus/fw-download.c
@@ -270,11 +270,11 @@ static int fw_download_fetch_firmware(struct gb_operation *op)
        struct gb_connection *connection = op->connection;
        struct fw_download *fw_download = gb_connection_get_data(connection);
        struct gb_fw_download_fetch_firmware_request *request;
-       struct gb_fw_download_fetch_firmware_response *response;
        struct fw_request *fw_req;
        const struct firmware *fw;
        unsigned int offset, size;
        u8 firmware_id;
+       u8 *response;
        int ret = 0;
 
        if (op->request->payload_size != sizeof(*request)) {
@@ -324,8 +324,8 @@ static int fw_download_fetch_firmware(struct gb_operation *op)
                goto put_fw;
        }
 
-       if (!gb_operation_response_alloc(op, sizeof(*response) + size,
-                                        GFP_KERNEL)) {
+       /* gb_fw_download_fetch_firmware_response contains only a byte array */
+       if (!gb_operation_response_alloc(op, size, GFP_KERNEL)) {
                dev_err(fw_download->parent,
                        "error allocating fetch firmware response\n");
                ret = -ENOMEM;
@@ -333,7 +333,7 @@ static int fw_download_fetch_firmware(struct gb_operation *op)
        }
 
        response = op->response->payload;
-       memcpy(response->data, fw->data + offset, size);
+       memcpy(response, fw->data + offset, size);
 
        dev_dbg(fw_download->parent,
                "responding with firmware (offs = %u, size = %u)\n", offset,

diff --git a/include/linux/greybus/greybus_protocols.h b/include/linux/greybus/greybus_protocols.h
index aeb8f9243545f10e777fbb05e694de1246b29ab8..820134b0105c2caf8cea3ff0985c92d48d3a2d4c 100644 (file)
--- a/include/linux/greybus/greybus_protocols.h
+++ b/include/linux/greybus/greybus_protocols.h
@@ -232,9 +232,7 @@ struct gb_fw_download_fetch_firmware_request {
        __le32                  size;
 } __packed;
 
-struct gb_fw_download_fetch_firmware_response {
-       __u8                    data[0];
-} __packed;
+/* gb_fw_download_fetch_firmware_response contains no other data */
 
 /* firmware download release firmware request */
 struct gb_fw_download_release_firmware_request {
@@ -414,9 +412,7 @@ struct gb_bootrom_get_firmware_request {
        __le32                  size;
 } __packed;
 
-struct gb_bootrom_get_firmware_response {
-       __u8                    data[0];
-} __packed;
+/* gb_bootrom_get_firmware_response contains no other data */
 
 /* Bootrom protocol Ready to boot request */
 struct gb_bootrom_ready_to_boot_request {