[PATCH v5 2/7] fpga: sec-mgr: enable secure updates

Russ Weight
2020-10-21T00:17:06Z

Extend the FPGA Security Manager class driver to
include an update/filename sysfs node that can be used
to initiate a security update. The filename of a secure
update file (BMC image, FPGA image, Root Entry Hash image,
or Code Signing Key cancellation image) can be written to
this sysfs entry to cause a secure update to occur.

The write of the filename will return immediately, and the
update will begin in the context of a kernel worker thread.
This tool utilizes the request_firmware framework, which
requires that the image file reside under /lib/firmware.

Signed-off-by: Russ Weight <russell.h.weight@intel.com>
Reviewed-by: Tom Rix <trix@redhat.com>
---
v5:
- When checking the return values for functions of type enum
fpga_sec_err err_code, test for FPGA_SEC_ERR_NONE instead of 0
v4:
- Changed from "Intel FPGA Security Manager" to FPGA Security Manager"
and removed unnecessary references to "Intel".
- Changed: iops -> sops, imgr -> smgr, IFPGA_ -> FPGA_, ifpga_ to fpga_
v3:
- Removed unnecessary "goto done"
- Added a comment to explain imgr->driver_unload in
ifpga_sec_mgr_unregister()
v2:
- Bumped documentation date and version
- Removed explicit value assignments in enums
- Other minor code cleanup per review comments
---
.../ABI/testing/sysfs-class-fpga-sec-mgr | 13 ++
drivers/fpga/fpga-sec-mgr.c | 164 ++++++++++++++++++
include/linux/fpga/fpga-sec-mgr.h | 49 ++++++
3 files changed, 226 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-fpga-sec-mgr b/Documentation/ABI/testing/sysfs-class-fpga-sec-mgr
index 843f0b58f171..5f10496b2a54 100644
--- a/Documentation/ABI/testing/sysfs-class-fpga-sec-mgr
+++ b/Documentation/ABI/testing/sysfs-class-fpga-sec-mgr
@@ -65,3 +65,16 @@ Contact: Russ Weight <russell.h.weight@intel.com>
Description: Read only. Returns number of times the user image for the
static region has been flashed.
Format: "%u".
+
+What: /sys/class/fpga_sec_mgr/fpga_secX/update/filename
+Date: Oct 2020
+KernelVersion: 5.11
+Contact: Russ Weight <russell.h.weight@intel.com>
+Description: Write only. Write the filename of an image
+ file to this sysfs file to initiate a secure
+ update. The file must have an appropriate header
+ which, among other things, identifies the target
+ for the update. This mechanism is used to update
+ BMC images, BMC firmware, Static Region images,
+ and Root Entry Hashes, and to cancel Code Signing
+ Keys (CSK).
diff --git a/drivers/fpga/fpga-sec-mgr.c b/drivers/fpga/fpga-sec-mgr.c
index 95b5a7ccbe44..8248b86ad098 100644
--- a/drivers/fpga/fpga-sec-mgr.c
+++ b/drivers/fpga/fpga-sec-mgr.c
@@ -5,8 +5,11 @@
* Copyright (C) 2019-2020 Intel Corporation, Inc.
*/

+#include <linux/delay.h>
+#include <linux/firmware.h>
#include <linux/fpga/fpga-sec-mgr.h>
#include <linux/idr.h>
+#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
@@ -18,6 +21,8 @@ struct fpga_sec_mgr_devres {
struct fpga_sec_mgr *smgr;
};

+#define WRITE_BLOCK_SIZE 0x4000 /* Update remaining_size every 0x4000 bytes */
+
#define to_sec_mgr(d) container_of(d, struct fpga_sec_mgr, dev)

static ssize_t
@@ -138,6 +143,94 @@ static struct attribute *sec_mgr_security_attrs[] = {
NULL,
};

+static void fpga_sec_dev_error(struct fpga_sec_mgr *smgr,
+ enum fpga_sec_err err_code)
+{
+ smgr->err_code = err_code;
+ smgr->sops->cancel(smgr);
+}
+
+static void progress_complete(struct fpga_sec_mgr *smgr)
+{
+ mutex_lock(&smgr->lock);
+ smgr->progress = FPGA_SEC_PROG_IDLE;
+ complete_all(&smgr->update_done);
+ mutex_unlock(&smgr->lock);
+}
+
+static void fpga_sec_mgr_update(struct work_struct *work)
+{
+ u32 size, blk_size, offset = 0;
+ struct fpga_sec_mgr *smgr;
+ const struct firmware *fw;
+ enum fpga_sec_err ret;
+
+ smgr = container_of(work, struct fpga_sec_mgr, work);
+
+ get_device(&smgr->dev);
+ if (request_firmware(&fw, smgr->filename, &smgr->dev)) {
+ smgr->err_code = FPGA_SEC_ERR_FILE_READ;
+ goto idle_exit;
+ }
+
+ smgr->data = fw->data;
+ smgr->remaining_size = fw->size;
+
+ if (!try_module_get(smgr->dev.parent->driver->owner)) {
+ smgr->err_code = FPGA_SEC_ERR_BUSY;
+ goto release_fw_exit;
+ }
+
+ smgr->progress = FPGA_SEC_PROG_PREPARING;
+ ret = smgr->sops->prepare(smgr);
+ if (ret != FPGA_SEC_ERR_NONE) {
+ fpga_sec_dev_error(smgr, ret);
+ goto modput_exit;
+ }
+
+ smgr->progress = FPGA_SEC_PROG_WRITING;
+ size = smgr->remaining_size;
+ while (size) {
+ blk_size = min_t(u32, size, WRITE_BLOCK_SIZE);
+ size -= blk_size;
+ ret = smgr->sops->write_blk(smgr, offset, blk_size);
+ if (ret != FPGA_SEC_ERR_NONE) {
+ fpga_sec_dev_error(smgr, ret);
+ goto done;
+ }
+
+ smgr->remaining_size = size;
+ offset += blk_size;
+ }
+
+ smgr->progress = FPGA_SEC_PROG_PROGRAMMING;
+ ret = smgr->sops->poll_complete(smgr);
+ if (ret != FPGA_SEC_ERR_NONE)
+ fpga_sec_dev_error(smgr, ret);
+
+done:
+ if (smgr->sops->cleanup)
+ smgr->sops->cleanup(smgr);
+
+modput_exit:
+ module_put(smgr->dev.parent->driver->owner);
+
+release_fw_exit:
+ smgr->data = NULL;
+ release_firmware(fw);
+
+idle_exit:
+ /*
+ * Note: smgr->remaining_size is left unmodified here to
+ * provide additional information on errors. It will be
+ * reinitialized when the next secure update begins.
+ */
+ kfree(smgr->filename);
+ smgr->filename = NULL;
+ put_device(&smgr->dev);
+ progress_complete(smgr);
+}
+
#define check_attr(attribute, _name) \
((attribute) == &dev_attr_##_name.attr && smgr->sops->_name)

@@ -168,6 +261,48 @@ static struct attribute_group sec_mgr_security_attr_group = {
.is_visible = sec_mgr_visible,
};

+static ssize_t filename_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct fpga_sec_mgr *smgr = to_sec_mgr(dev);
+ int ret = count;
+
+ if (count == 0 || count >= PATH_MAX)
+ return -EINVAL;
+
+ mutex_lock(&smgr->lock);
+ if (smgr->driver_unload || smgr->progress != FPGA_SEC_PROG_IDLE) {
+ ret = -EBUSY;
+ goto unlock_exit;
+ }
+
+ smgr->filename = kstrndup(buf, count - 1, GFP_KERNEL);
+ if (!smgr->filename) {
+ ret = -ENOMEM;
+ goto unlock_exit;
+ }
+
+ smgr->err_code = FPGA_SEC_ERR_NONE;
+ smgr->progress = FPGA_SEC_PROG_READING;
+ reinit_completion(&smgr->update_done);
+ schedule_work(&smgr->work);
+
+unlock_exit:
+ mutex_unlock(&smgr->lock);
+ return ret;
+}
+static DEVICE_ATTR_WO(filename);
+
+static struct attribute *sec_mgr_update_attrs[] = {
+ &dev_attr_filename.attr,
+ NULL,
+};
+
+static struct attribute_group sec_mgr_update_attr_group = {
+ .name = "update",
+ .attrs = sec_mgr_update_attrs,
+};
+
static ssize_t name_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -189,6 +324,7 @@ static struct attribute_group sec_mgr_attr_group = {
static const struct attribute_group *fpga_sec_mgr_attr_groups[] = {
&sec_mgr_attr_group,
&sec_mgr_security_attr_group,
+ &sec_mgr_update_attr_group,
NULL,
};

@@ -247,6 +383,12 @@ fpga_sec_mgr_create(struct device *dev, const char *name,
struct fpga_sec_mgr *smgr;
int id, ret;

+ if (!sops || !sops->cancel || !sops->prepare ||
+ !sops->write_blk || !sops->poll_complete) {
+ dev_err(dev, "Attempt to register without required ops\n");
+ return NULL;
+ }
+
if (!check_reh_handler(dev, sops, bmc) ||
!check_reh_handler(dev, sops, sr) ||
!check_reh_handler(dev, sops, pr) ||
@@ -274,6 +416,8 @@ fpga_sec_mgr_create(struct device *dev, const char *name,
smgr->name = name;
smgr->priv = priv;
smgr->sops = sops;
+ init_completion(&smgr->update_done);
+ INIT_WORK(&smgr->work, fpga_sec_mgr_update);

device_initialize(&smgr->dev);
smgr->dev.class = fpga_sec_mgr_class;
@@ -391,11 +535,31 @@ EXPORT_SYMBOL_GPL(fpga_sec_mgr_register);
*
* This function is intended for use in an FPGA security manager
* driver's remove() function.
+ *
+ * For some devices, once the secure update has begun authentication
+ * the hardware cannot be signaled to stop, and the driver will not
+ * exit until the hardware signals completion. This could be 30+
+ * minutes of waiting. The driver_unload flag enableds a force-unload
+ * of the driver (e.g. modprobe -r) by signaling the parent driver to
+ * exit even if the hardware update is incomplete. The driver_unload
+ * flag also prevents new updates from starting once the unregister
+ * process has begun.
*/
void fpga_sec_mgr_unregister(struct fpga_sec_mgr *smgr)
{
dev_info(&smgr->dev, "%s %s\n", __func__, smgr->name);

+ mutex_lock(&smgr->lock);
+ smgr->driver_unload = true;
+ if (smgr->progress == FPGA_SEC_PROG_IDLE) {
+ mutex_unlock(&smgr->lock);
+ goto unregister;
+ }
+
+ mutex_unlock(&smgr->lock);
+ wait_for_completion(&smgr->update_done);
+
+unregister:
device_unregister(&smgr->dev);
}
EXPORT_SYMBOL_GPL(fpga_sec_mgr_unregister);
diff --git a/include/linux/fpga/fpga-sec-mgr.h b/include/linux/fpga/fpga-sec-mgr.h
index dd596c6c3748..d2e482456d16 100644
--- a/include/linux/fpga/fpga-sec-mgr.h
+++ b/include/linux/fpga/fpga-sec-mgr.h
@@ -7,12 +7,26 @@
#ifndef _LINUX_FPGA_SEC_MGR_H
#define _LINUX_FPGA_SEC_MGR_H

+#include <linux/completion.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/types.h>

struct fpga_sec_mgr;

+enum fpga_sec_err {
+ FPGA_SEC_ERR_NONE,
+ FPGA_SEC_ERR_HW_ERROR,
+ FPGA_SEC_ERR_TIMEOUT,
+ FPGA_SEC_ERR_CANCELED,
+ FPGA_SEC_ERR_BUSY,
+ FPGA_SEC_ERR_INVALID_SIZE,
+ FPGA_SEC_ERR_RW_ERROR,
+ FPGA_SEC_ERR_WEAROUT,
+ FPGA_SEC_ERR_FILE_READ,
+ FPGA_SEC_ERR_MAX
+};
+
/**
* struct fpga_sec_mgr_ops - device specific operations
* @user_flash_count: Optional: Return sysfs string output for FPGA
@@ -35,6 +49,17 @@ struct fpga_sec_mgr;
* @bmc_reh_size: Optional: Return byte size for BMC root entry hash
* @sr_reh_size: Optional: Return byte size for SR root entry hash
* @pr_reh_size: Optional: Return byte size for PR root entry hash
+ * @prepare: Required: Prepare secure update
+ * @write_blk: Required: Write a block of data
+ * @poll_complete: Required: Check for the completion of the
+ * HW authentication/programming process. This
+ * function should check for smgr->driver_unload
+ * and abort with FPGA_SEC_ERR_CANCELED when true.
+ * @cancel: Required: Signal HW to cancel update
+ * @cleanup: Optional: Complements the prepare()
+ * function and is called at the completion
+ * of the update, whether success or failure,
+ * if the prepare function succeeded.
*/
struct fpga_sec_mgr_ops {
int (*user_flash_count)(struct fpga_sec_mgr *smgr);
@@ -56,6 +81,22 @@ struct fpga_sec_mgr_ops {
int (*bmc_canceled_csk_nbits)(struct fpga_sec_mgr *smgr);
int (*sr_canceled_csk_nbits)(struct fpga_sec_mgr *smgr);
int (*pr_canceled_csk_nbits)(struct fpga_sec_mgr *smgr);
+ enum fpga_sec_err (*prepare)(struct fpga_sec_mgr *smgr);
+ enum fpga_sec_err (*write_blk)(struct fpga_sec_mgr *smgr,
+ u32 offset, u32 size);
+ enum fpga_sec_err (*poll_complete)(struct fpga_sec_mgr *smgr);
+ void (*cleanup)(struct fpga_sec_mgr *smgr);
+ enum fpga_sec_err (*cancel)(struct fpga_sec_mgr *smgr);
+};
+
+/* Update progress codes */
+enum fpga_sec_prog {
+ FPGA_SEC_PROG_IDLE,
+ FPGA_SEC_PROG_READING,
+ FPGA_SEC_PROG_PREPARING,
+ FPGA_SEC_PROG_WRITING,
+ FPGA_SEC_PROG_PROGRAMMING,
+ FPGA_SEC_PROG_MAX
};

struct fpga_sec_mgr {
@@ -63,6 +104,14 @@ struct fpga_sec_mgr {
struct device dev;
const struct fpga_sec_mgr_ops *sops;
struct mutex lock; /* protect data structure contents */
+ struct work_struct work;
+ struct completion update_done;
+ char *filename;
+ const u8 *data; /* pointer to update data */
+ u32 remaining_size; /* size remaining to transfer */
+ enum fpga_sec_prog progress;
+ enum fpga_sec_err err_code; /* security manager error code */
+ bool driver_unload;
void *priv;
};

--
2.25.1