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

Kees Cook
2024-02-16T23:28:27Z

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>
---
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;
--
2.34.1