[greybus-dev] Re: [PATCH] greybus: Avoid fake flexible array for response data

On 2/16/24 5:28 PM, Kees Cook wrote:

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.

The only down side I see is that it sort of disrupts a pattern used on Greybus request handlers (and the response structure definitions).

I think a one-line comment in place of each of these two definitions would be helpful, something like: /* gb_fw_download_fetch_firmware_response contains no data */

And then add a similar comment above the calls to gb_operation_response_alloc().

Otherwise this looks good.

Reviewed-by: Alex Elder elder@linaro.org

Signed-off-by: Kees Cook keescook@chromium.org

Cc: Viresh Kumar vireshk@kernel.org Cc: Johan Hovold johan@kernel.org Cc: Alex Elder elder@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Gustavo A. R. Silva gustavo@embeddedor.com Cc: greybus-dev@lists.linaro.org Cc: linux-staging@lists.linux.dev

---

drivers/staging/greybus/bootrom.c | 7 +++---- drivers/staging/greybus/fw-download.c | 7 +++---- include/linux/greybus/greybus_protocols.h | 8 -------- 3 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/drivers/staging/greybus/bootrom.c b/drivers/staging/greybus/bootrom.c index 79581457c4af..76ad5f289072 100644 --- 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 +280,14 @@ static int gb_bootrom_get_firmware(struct gb_operation *op) goto unlock; }

• if (!gb_operation_response_alloc(op, sizeof(*firmware_response) + size,

• 			 GFP_KERNEL)) {
  

• 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 543692c567f9..2d73bb729aa2 100644 --- a/drivers/staging/greybus/fw-download.c +++ b/drivers/staging/greybus/fw-download.c @@ -271,11 +271,11 @@ 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)) { @@ -325,8 +325,7 @@ static int fw_download_fetch_firmware(struct gb_operation *op) goto put_fw; }

• if (!gb_operation_response_alloc(op, sizeof(*response) + size,

• 			 GFP_KERNEL)) {
  

• if (!gb_operation_response_alloc(op, size, GFP_KERNEL)) { dev_err(fw_download->parent, "error allocating fetch firmware response\n"); ret = -ENOMEM;

@@ -334,7 +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 aeb8f9243545..603acdcc0c6b 100644 --- a/include/linux/greybus/greybus_protocols.h +++ b/include/linux/greybus/greybus_protocols.h @@ -232,10 +232,6 @@ struct gb_fw_download_fetch_firmware_request { __le32 size; } __packed; -struct gb_fw_download_fetch_firmware_response {

• __u8 data[0];

-} __packed;

• /* firmware download release firmware request */ struct gb_fw_download_release_firmware_request { __u8 firmware_id;

@@ -414,10 +410,6 @@ struct gb_bootrom_get_firmware_request { __le32 size; } __packed; -struct gb_bootrom_get_firmware_response {

• __u8 data[0];

-} __packed;

• /* Bootrom protocol Ready to boot request */ struct gb_bootrom_ready_to_boot_request { __u8 status;