ptp: ocp: Add firmware header checks

Right now it's possible to flash any kind of binary via devlink and
break the card easily. This diff adds an optional header check when
installing the firmware.
Signed-off-by: Vadim Fedorenko <vadfed@fb.com>
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/ptp/ptp_ocp.c

@@ -19,6 +19,7 @@
 #include <linux/i2c.h>
 #include <linux/mtd/mtd.h>
 #include <linux/nvmem-consumer.h>
+#include <linux/crc16.h>
 
 #define PCI_VENDOR_ID_FACEBOOK			0x1d9b
 #define PCI_DEVICE_ID_FACEBOOK_TIMECARD		0x0400
@@ -213,6 +214,17 @@ struct ptp_ocp_flash_info {
 	void *data;
 };
 
+struct ptp_ocp_firmware_header {
+	char magic[4];
+	__be16 pci_vendor_id;
+	__be16 pci_device_id;
+	__be32 image_size;
+	__be16 hw_revision;
+	__be16 crc;
+};
+
+#define OCP_FIRMWARE_MAGIC_HEADER "OCPC"
+
 struct ptp_ocp_i2c_info {
 	const char *name;
 	unsigned long fixed_rate;
@@ -1323,25 +1335,81 @@ ptp_ocp_find_flash(struct ptp_ocp *bp)
 	return dev;
 }
 
+static int
+ptp_ocp_devlink_fw_image(struct devlink *devlink, const struct firmware *fw,
+			 const u8 **data, size_t *size)
+{
+	struct ptp_ocp *bp = devlink_priv(devlink);
+	const struct ptp_ocp_firmware_header *hdr;
+	size_t offset, length;
+	u16 crc;
+
+	hdr = (const struct ptp_ocp_firmware_header *)fw->data;
+	if (memcmp(hdr->magic, OCP_FIRMWARE_MAGIC_HEADER, 4)) {
+		devlink_flash_update_status_notify(devlink,
+			"No firmware header found, flashing raw image",
+			NULL, 0, 0);
+		offset = 0;
+		length = fw->size;
+		goto out;
+	}
+
+	if (be16_to_cpu(hdr->pci_vendor_id) != bp->pdev->vendor ||
+	    be16_to_cpu(hdr->pci_device_id) != bp->pdev->device) {
+		devlink_flash_update_status_notify(devlink,
+			"Firmware image compatibility check failed",
+			NULL, 0, 0);
+		return -EINVAL;
+	}
+
+	offset = sizeof(*hdr);
+	length = be32_to_cpu(hdr->image_size);
+	if (length != (fw->size - offset)) {
+		devlink_flash_update_status_notify(devlink,
+			"Firmware image size check failed",
+			NULL, 0, 0);
+		return -EINVAL;
+	}
+
+	crc = crc16(0xffff, &fw->data[offset], length);
+	if (be16_to_cpu(hdr->crc) != crc) {
+		devlink_flash_update_status_notify(devlink,
+			"Firmware image CRC check failed",
+			NULL, 0, 0);
+		return -EINVAL;
+	}
+
+out:
+	*data = &fw->data[offset];
+	*size = length;
+
+	return 0;
+}
+
 static int
 ptp_ocp_devlink_flash(struct devlink *devlink, struct device *dev,
 		      const struct firmware *fw)
 {
 	struct mtd_info *mtd = dev_get_drvdata(dev);
 	struct ptp_ocp *bp = devlink_priv(devlink);
-	size_t off, len, resid, wrote;
+	size_t off, len, size, resid, wrote;
 	struct erase_info erase;
 	size_t base, blksz;
-	int err = 0;
+	const u8 *data;
+	int err;
+
+	err = ptp_ocp_devlink_fw_image(devlink, fw, &data, &size);
+	if (err)
+		goto out;
 
 	off = 0;
 	base = bp->flash_start;
 	blksz = 4096;
-	resid = fw->size;
+	resid = size;
 
 	while (resid) {
 		devlink_flash_update_status_notify(devlink, "Flashing",
-						   NULL, off, fw->size);
+						   NULL, off, size);
 
 		len = min_t(size_t, resid, blksz);
 		erase.addr = base + off;
@@ -1351,7 +1419,7 @@ ptp_ocp_devlink_flash(struct devlink *devlink, struct device *dev,
 		if (err)
 			goto out;
 
-		err = mtd_write(mtd, base + off, len, &wrote, &fw->data[off]);
+		err = mtd_write(mtd, base + off, len, &wrote, data + off);
 		if (err)
 			goto out;