* All Rights Reserved.
*
* This file is released under the GPL.
- *
+ */
+/*
* Implements a Chrome OS platform specific error handler.
+ * When verity detects an invalid block, this error handling will
+ * attempt to corrupt the kernel boot image. On reboot, the bios will
+ * detect the kernel corruption and switch to the alternate kernel
+ * and root file system partitions.
+ *
+ * Assumptions:
+ * 1. Partitions are specified on the command line using uuid.
+ * 2. The kernel partition is the partition number is one less
+ * than the root partition number.
*/
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/notifier.h>
+#include <linux/string.h>
#include <asm/page.h>
#include "dm-verity.h"
return 0;
}
+static char *get_info_from_cmdline(const char *key)
+{
+ const char *dev;
+ const char *end;
+ int len;
+
+ dev = strstr(saved_command_line, key);
+ if (!dev)
+ return NULL;
+ len = strlen(key);
+ dev = &dev[len];
+ end = strchr(dev, ' ');
+ return kstrndup(dev, end - dev, GFP_ATOMIC);
+}
+
+/**
+ * match_dev_by_uuid - callback for finding a partition using its uuid
+ * @dev: device passed in by the caller
+ * @uuid_data: opaque pointer to a uuid packed by part_pack_uuid().
+ *
+ * Returns 1 if the device matches, and 0 otherwise.
+ */
+static int match_dev_by_uuid(struct device *dev, void *uuid_data)
+{
+ u8 *uuid = uuid_data;
+ struct hd_struct *part = dev_to_part(dev);
+
+ if (!part->info)
+ goto no_match;
+
+ if (memcmp(uuid, part->info->uuid, sizeof(part->info->uuid)))
+ goto no_match;
+
+ return 1;
+no_match:
+ return 0;
+}
+
+static dev_t get_boot_dev_from_root_dev(struct block_device *root_bdev)
+{
+ /* Very basic sanity checking. This should be better. */
+ if (!root_bdev || !root_bdev->bd_part ||
+ MAJOR(root_bdev->bd_dev) == 254 ||
+ root_bdev->bd_part->partno <= 1) {
+ return 0;
+ }
+ return MKDEV(MAJOR(root_bdev->bd_dev), MINOR(root_bdev->bd_dev) - 1);
+}
+
+/* get_boot_dev is bassed on dm_get_device_by_uuid in dm_bootcache. */
+static dev_t get_boot_dev(void)
+{
+ const char *uuid_str;
+ struct device *dev = NULL;
+ dev_t devt = 0;
+ u8 uuid[16];
+ size_t uuid_length;
+
+ uuid_str = get_info_from_cmdline(" kern_guid=");
+ if (!uuid_str) {
+ DMERR("Couldn't get uuid, try root dev");
+ return 0;
+ }
+ uuid_length = strlen(uuid_str);
+ if (uuid_length != 36)
+ goto bad_uuid;
+ /* Pack the requested UUID in the expected format. */
+ part_pack_uuid(uuid_str, uuid);
+
+ dev = class_find_device(&block_class, NULL, uuid, &match_dev_by_uuid);
+ if (!dev)
+ goto found_nothing;
+
+ devt = dev->devt;
+ put_device(dev);
+
+ return devt;
+
+bad_uuid:
+ kfree(uuid_str);
+ DMDEBUG("Supplied value '%s' is an invalid UUID", uuid_str);
+ return 0;
+found_nothing:
+ kfree(uuid_str);
+ DMDEBUG("No matching partition for GUID: %s", uuid_str);
+ return 0;
+}
+
/* Replaces the first 8 bytes of a partition with DMVERROR */
static int chromeos_invalidate_kernel(struct block_device *root_bdev)
{
struct block_device *bdev;
struct bio *bio;
struct page *page;
- int partno = root_bdev->bd_part->partno - 1;
- dev_t kdev = MKDEV(0, 0);
+ dev_t devt;
fmode_t dev_mode;
/* Ensure we do synchronous unblocked I/O. We may also need
* sync_bdev() on completion, but it really shouldn't.
*/
int rw = REQ_SYNC | REQ_SOFTBARRIER | REQ_NOIDLE;
- /* Very basic sanity checking. This should be better. */
- if (!root_bdev || !root_bdev->bd_part ||
- root_bdev->bd_part->partno <= 1) {
- DMERR("invalidate_kernel: partition layout unexpected");
- return -EINVAL;
+ devt = get_boot_dev_from_root_dev(root_bdev);
+ if (!devt) {
+ devt = get_boot_dev();
+ if (!devt)
+ return -EINVAL;
}
- kdev = MKDEV(MAJOR(root_bdev->bd_dev), MINOR(root_bdev->bd_dev) - 1);
-
- DMERR("Attempting to invalidate kernel (part:%d,devt:%d)",
- partno, kdev);
/* First we open the device for reading. */
dev_mode = FMODE_READ | FMODE_EXCL;
- bdev = blkdev_get_by_dev(kdev, dev_mode, chromeos_invalidate_kernel);
+ bdev = blkdev_get_by_dev(devt, dev_mode, chromeos_invalidate_kernel);
if (IS_ERR(bdev)) {
DMERR("invalidate_kernel: could not open device for reading");
+ dev_mode = 0;
ret = -1;
goto failed_to_read;
}
/* The block dev was being changed on read. Let's reopen here. */
blkdev_put(bdev, dev_mode);
dev_mode = FMODE_WRITE | FMODE_EXCL;
- bdev = blkdev_get_by_dev(kdev, dev_mode, chromeos_invalidate_kernel);
+ bdev = blkdev_get_by_dev(devt, dev_mode, chromeos_invalidate_kernel);
if (IS_ERR(bdev)) {
DMERR("invalidate_kernel: could not open device for reading");
dev_mode = 0;
projects / cascardo / linux.git / blobdiff