From 7fe7b0acdfcb3b099593c5fc6d9b72c9a9cefb86 Mon Sep 17 00:00:00 2001 From: David Zeuthen Date: Tue, 24 Jan 2017 13:17:01 -0500 Subject: [PATCH] ANDROID: AVB error handler to invalidate vbmeta partition. If androidboot.vbmeta.invalidate_on_error is 'yes' and androidboot.vbmeta.device is set and points to a device with vbmeta magic, this header will be overwritten upon an irrecoverable dm-verity error. The side-effect of this is that the slot will fail to verify on next reboot, effectively triggering the boot loader to fallback to another slot. This work both if the vbmeta struct is at the start of a partition or if there's an AVB footer at the end. This code is based on drivers/md/dm-verity-chromeos.c from ChromiumOS. Bug: 31622239 Bug: 120445368 Test: Manually tested (other arch). Signed-off-by: David Zeuthen [astrachan: re-diffed against a kernel without dm-android-verity] Change-Id: I571b5a75461da38ad832a9bea33c298bef859e26 Signed-off-by: Alistair Strachan --- drivers/md/Kconfig | 9 ++ drivers/md/Makefile | 4 + drivers/md/dm-verity-avb.c | 229 ++++++++++++++++++++++++++++++++++ drivers/md/dm-verity-target.c | 6 +- drivers/md/dm-verity.h | 2 + 5 files changed, 249 insertions(+), 1 deletion(-) create mode 100644 drivers/md/dm-verity-avb.c diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig index 8b8c123cae66..c3a821a598c5 100644 --- a/drivers/md/Kconfig +++ b/drivers/md/Kconfig @@ -479,6 +479,15 @@ config DM_VERITY If unsure, say N. +config DM_VERITY_AVB + tristate "Support AVB specific verity error behavior" + depends on DM_VERITY + ---help--- + Enables Android Verified Boot platform-specific error + behavior. In particular, it will modify the vbmeta partition + specified on the kernel command-line when non-transient error + occurs (followed by a panic). + config DM_VERITY_FEC bool "Verity forward error correction support" depends on DM_VERITY diff --git a/drivers/md/Makefile b/drivers/md/Makefile index 822f4e8753bc..0aad838c6990 100644 --- a/drivers/md/Makefile +++ b/drivers/md/Makefile @@ -73,6 +73,10 @@ ifeq ($(CONFIG_DM_UEVENT),y) dm-mod-objs += dm-uevent.o endif +ifeq ($(CONFIG_DM_VERITY_AVB),y) +dm-verity-objs += dm-verity-avb.o +endif + ifeq ($(CONFIG_DM_VERITY_FEC),y) dm-verity-objs += dm-verity-fec.o endif diff --git a/drivers/md/dm-verity-avb.c b/drivers/md/dm-verity-avb.c new file mode 100644 index 000000000000..a9f102aa379e --- /dev/null +++ b/drivers/md/dm-verity-avb.c @@ -0,0 +1,229 @@ +/* + * Copyright (C) 2017 Google. + * + * This file is released under the GPLv2. + * + * Based on drivers/md/dm-verity-chromeos.c + */ + +#include +#include +#include + +#define DM_MSG_PREFIX "verity-avb" + +/* Set via module parameters. */ +static char avb_vbmeta_device[64]; +static char avb_invalidate_on_error[4]; + +static void invalidate_vbmeta_endio(struct bio *bio) +{ + if (bio->bi_status) + DMERR("invalidate_vbmeta_endio: error %d", bio->bi_status); + complete(bio->bi_private); +} + +static int invalidate_vbmeta_submit(struct bio *bio, + struct block_device *bdev, + int op, int access_last_sector, + struct page *page) +{ + DECLARE_COMPLETION_ONSTACK(wait); + + bio->bi_private = &wait; + bio->bi_end_io = invalidate_vbmeta_endio; + bio_set_dev(bio, bdev); + bio_set_op_attrs(bio, op, REQ_SYNC); + + bio->bi_iter.bi_sector = 0; + if (access_last_sector) { + sector_t last_sector; + + last_sector = (i_size_read(bdev->bd_inode)>>SECTOR_SHIFT) - 1; + bio->bi_iter.bi_sector = last_sector; + } + if (!bio_add_page(bio, page, PAGE_SIZE, 0)) { + DMERR("invalidate_vbmeta_submit: bio_add_page error"); + return -EIO; + } + + submit_bio(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 access_last_sector = 0; + + DMINFO("invalidate_vbmeta: acting on device %d:%d", + MAJOR(vbmeta_devt), MINOR(vbmeta_devt)); + + /* 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, REQ_OP_READ, + 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<bi_remaining. + */ + bio_reset(bio); + + ret = invalidate_vbmeta_submit(bio, bdev, REQ_OP_WRITE, + 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 (strcmp(avb_invalidate_on_error, "yes") != 0) { + DMINFO("Not configured to invalidate"); + return; + } + + 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 "); +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); +module_param_string(invalidate_on_error, avb_invalidate_on_error, + sizeof(avb_invalidate_on_error), 0); diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c index fc65f0dedf7f..0bb39cc34747 100644 --- a/drivers/md/dm-verity-target.c +++ b/drivers/md/dm-verity-target.c @@ -251,8 +251,12 @@ static int verity_handle_err(struct dm_verity *v, enum verity_block_type type, if (v->mode == DM_VERITY_MODE_LOGGING) return 0; - if (v->mode == DM_VERITY_MODE_RESTART) + if (v->mode == DM_VERITY_MODE_RESTART) { +#ifdef CONFIG_DM_VERITY_AVB + dm_verity_avb_error_handler(); +#endif kernel_restart("dm-verity device corrupted"); + } return 1; } diff --git a/drivers/md/dm-verity.h b/drivers/md/dm-verity.h index 3441c10b840c..0152d36bd91c 100644 --- a/drivers/md/dm-verity.h +++ b/drivers/md/dm-verity.h @@ -127,4 +127,6 @@ extern int verity_hash(struct dm_verity *v, struct ahash_request *req, extern int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io, sector_t block, u8 *digest, bool *is_zero); +extern void dm_verity_avb_error_handler(void); + #endif /* DM_VERITY_H */