1 files changed, 217 insertions, 0 deletions

diff --git a/drivers/md/dm-verity-avb.c b/drivers/md/dm-verity-avb.c
new file mode 100644
index 000000000000..88487346c4c6
--- /dev/null
+++ b/drivers/md/dm-verity-avb.c
@@ -0,0 +1,217 @@
+/*
+ * Copyright (C) 2017 Google.
+ *
+ * This file is released under the GPLv2.
+ *
+ * Based on drivers/md/dm-verity-chromeos.c
+ */
+
+#include <linux/device-mapper.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+
+#define DM_MSG_PREFIX "verity-avb"
+
+/* Set via module parameter. */
+static char avb_vbmeta_device[64];
+
+static void invalidate_vbmeta_endio(struct bio *bio)
+{
+        complete(bio->bi_private);
+}
+
+static int invalidate_vbmeta_submit(struct bio *bio,
+                                    struct block_device *bdev,
+                                    int rw, int access_last_sector,
+                                    struct page *page)
+{
+        DECLARE_COMPLETION_ONSTACK(wait);
+
+        bio->bi_private = &wait;
+        bio->bi_end_io = invalidate_vbmeta_endio;
+        bio->bi_bdev = bdev;
+
+        bio->bi_iter.bi_sector = 0;
+        if (access_last_sector) {
+                sector_t last_sector = (i_size_read(bdev->bd_inode)>>SECTOR_SHIFT) - 1;
+                bio->bi_iter.bi_sector = last_sector;
+        }
+        bio->bi_vcnt = 1;
+        bio->bi_iter.bi_idx = 0;
+        bio->bi_iter.bi_size = 512;
+        bio->bi_iter.bi_bvec_done = 0;
+        bio->bi_rw = rw;
+        bio->bi_io_vec[0].bv_page = page;
+        bio->bi_io_vec[0].bv_len = 512;
+        bio->bi_io_vec[0].bv_offset = 0;
+
+        submit_bio(rw, bio);
+        /* Wait up to 2 seconds for completion or fail. */
+        if (!wait_for_completion_timeout(&wait, msecs_to_jiffies(2000)))
+                return -EIO;
+        return 0;
+}
+
+static int invalidate_vbmeta(dev_t vbmeta_devt)
+{
+        int ret = 0;
+        struct block_device *bdev;
+        struct bio *bio;
+        struct page *page;
+        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;
+        int access_last_sector = 0;
+
+        /* First we open the device for reading. */
+        dev_mode = FMODE_READ | FMODE_EXCL;
+        bdev = blkdev_get_by_dev(vbmeta_devt, dev_mode,
+                                 invalidate_vbmeta);
+        if (IS_ERR(bdev)) {
+                DMERR("invalidate_kernel: could not open device for reading");
+                dev_mode = 0;
+                ret = -ENOENT;
+                goto failed_to_read;
+        }
+
+        bio = bio_alloc(GFP_NOIO, 1);
+        if (!bio) {
+                ret = -ENOMEM;
+                goto failed_bio_alloc;
+        }
+
+        page = alloc_page(GFP_NOIO);
+        if (!page) {
+                ret = -ENOMEM;
+                goto failed_to_alloc_page;
+        }
+
+        access_last_sector = 0;
+        ret = invalidate_vbmeta_submit(bio, bdev, rw, access_last_sector, page);
+        if (ret) {
+                DMERR("invalidate_vbmeta: error reading");
+                goto failed_to_submit_read;
+        }
+
+        /* We have a page. Let's make sure it looks right. */
+        if (memcmp("AVB0", page_address(page), 4) == 0) {
+                /* Stamp it. */
+                memcpy(page_address(page), "AVE0", 4);
+                DMINFO("invalidate_vbmeta: found vbmeta partition");
+        } else {
+                /* Could be this is on a AVB footer, check. Also, since the
+                 * AVB footer is in the last 64 bytes, adjust for the fact that
+                 * we're dealing with 512-byte sectors.
+                 */
+                size_t offset = (1<<SECTOR_SHIFT) - 64;
+
+                access_last_sector = 1;
+                ret = invalidate_vbmeta_submit(bio, bdev, rw,
+                                               access_last_sector, page);
+                if (ret) {
+                        DMERR("invalidate_vbmeta: error reading");
+                        goto failed_to_submit_read;
+                }
+                if (memcmp("AVBf", page_address(page) + offset, 4) != 0) {
+                        DMERR("invalidate_vbmeta called on non-vbmeta partition");
+                        ret = -EINVAL;
+                        goto invalid_header;
+                }
+                /* Stamp it. */
+                memcpy(page_address(page) + offset, "AVE0", 4);
+                DMINFO("invalidate_vbmeta: found vbmeta footer partition");
+        }
+
+        /* Now rewrite the changed page - 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(vbmeta_devt, dev_mode,
+                                 invalidate_vbmeta);
+        if (IS_ERR(bdev)) {
+                DMERR("invalidate_vbmeta: could not open device for writing");
+                dev_mode = 0;
+                ret = -ENOENT;
+                goto failed_to_write;
+        }
+
+        /* We re-use the same bio to do the write after the read. Need to reset
+         * it to initialize bio->bi_remaining.
+         */
+        bio_reset(bio);
+
+        rw |= REQ_WRITE;
+        ret = invalidate_vbmeta_submit(bio, bdev, rw, access_last_sector, page);
+        if (ret) {
+                DMERR("invalidate_vbmeta: error writing");
+                goto failed_to_submit_write;
+        }
+
+        DMERR("invalidate_vbmeta: completed.");
+        ret = 0;
+failed_to_submit_write:
+failed_to_write:
+invalid_header:
+        __free_page(page);
+failed_to_submit_read:
+        /* Technically, we'll leak a page with the pending bio, but
+         * we're about to reboot anyway.
+         */
+failed_to_alloc_page:
+        bio_put(bio);
+failed_bio_alloc:
+        if (dev_mode)
+                blkdev_put(bdev, dev_mode);
+failed_to_read:
+        return ret;
+}
+
+void dm_verity_avb_error_handler(void)
+{
+        dev_t dev;
+
+        DMINFO("AVB error handler called for %s", avb_vbmeta_device);
+
+        if (avb_vbmeta_device[0] == '\0') {
+                DMERR("avb_vbmeta_device parameter not set");
+                goto fail_no_dev;
+        }
+
+        dev = name_to_dev_t(avb_vbmeta_device);
+        if (!dev) {
+                DMERR("No matching partition for device: %s",
+                      avb_vbmeta_device);
+                goto fail_no_dev;
+        }
+
+        invalidate_vbmeta(dev);
+
+fail_no_dev:
+        ;
+}
+
+static int __init dm_verity_avb_init(void)
+{
+        DMINFO("AVB error handler initialized with vbmeta device: %s",
+               avb_vbmeta_device);
+        return 0;
+}
+
+static void __exit dm_verity_avb_exit(void)
+{
+}
+
+module_init(dm_verity_avb_init);
+module_exit(dm_verity_avb_exit);
+
+MODULE_AUTHOR("David Zeuthen <zeuthen@google.com>");
+MODULE_DESCRIPTION("AVB-specific error handler for dm-verity");
+MODULE_LICENSE("GPL");
+
+/* Declare parameter with no module prefix */
+#undef MODULE_PARAM_PREFIX
+#define MODULE_PARAM_PREFIX     "androidboot.vbmeta."
+module_param_string(device, avb_vbmeta_device, sizeof(avb_vbmeta_device), 0);