linux/drivers/md/dm-verity-target.c
Wu Bo 0193e3966c dm verity: don't perform FEC for failed readahead IO
We found an issue under Android OTA scenario that many BIOs have to do
FEC where the data under dm-verity is 100% complete and no corruption.

Android OTA has many dm-block layers, from upper to lower:
dm-verity
dm-snapshot
dm-origin & dm-cow
dm-linear
ufs

DM tables have to change 2 times during Android OTA merging process.
When doing table change, the dm-snapshot will be suspended for a while.
During this interval, many readahead IOs are submitted to dm_verity
from filesystem. Then the kverity works are busy doing FEC process
which cost too much time to finish dm-verity IO. This causes needless
delay which feels like system is hung.

After adding debugging it was found that each readahead IO needed
around 10s to finish when this situation occurred. This is due to IO
amplification:

dm-snapshot suspend
erofs_readahead     // 300+ io is submitted
	dm_submit_bio (dm_verity)
		dm_submit_bio (dm_snapshot)
		bio return EIO
		bio got nothing, it's empty
	verity_end_io
	verity_verify_io
	forloop range(0, io->n_blocks)    // each io->nblocks ~= 20
		verity_fec_decode
		fec_decode_rsb
		fec_read_bufs
		forloop range(0, v->fec->rsn) // v->fec->rsn = 253
			new_read
			submit_bio (dm_snapshot)
		end loop
	end loop
dm-snapshot resume

Readahead BIOs get nothing while dm-snapshot is suspended, so all of
them will cause verity's FEC.
Each readahead BIO needs to verify ~20 (io->nblocks) blocks.
Each block needs to do FEC, and every block needs to do 253
(v->fec->rsn) reads.
So during the suspend interval(~200ms), 300 readahead BIOs trigger
~1518000 (300*20*253) IOs to dm-snapshot.

As readahead IO is not required by userspace, and to fix this issue,
it is best to pass readahead errors to upper layer to handle it.

Cc: stable@vger.kernel.org
Fixes: a739ff3f54 ("dm verity: add support for forward error correction")
Signed-off-by: Wu Bo <bo.wu@vivo.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
2023-11-29 12:55:31 -05:00

1528 lines
37 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2012 Red Hat, Inc.
*
* Author: Mikulas Patocka <mpatocka@redhat.com>
*
* Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
*
* In the file "/sys/module/dm_verity/parameters/prefetch_cluster" you can set
* default prefetch value. Data are read in "prefetch_cluster" chunks from the
* hash device. Setting this greatly improves performance when data and hash
* are on the same disk on different partitions on devices with poor random
* access behavior.
*/
#include "dm-verity.h"
#include "dm-verity-fec.h"
#include "dm-verity-verify-sig.h"
#include "dm-audit.h"
#include <linux/module.h>
#include <linux/reboot.h>
#include <linux/scatterlist.h>
#include <linux/string.h>
#include <linux/jump_label.h>
#define DM_MSG_PREFIX "verity"
#define DM_VERITY_ENV_LENGTH 42
#define DM_VERITY_ENV_VAR_NAME "DM_VERITY_ERR_BLOCK_NR"
#define DM_VERITY_DEFAULT_PREFETCH_SIZE 262144
#define DM_VERITY_MAX_CORRUPTED_ERRS 100
#define DM_VERITY_OPT_LOGGING "ignore_corruption"
#define DM_VERITY_OPT_RESTART "restart_on_corruption"
#define DM_VERITY_OPT_PANIC "panic_on_corruption"
#define DM_VERITY_OPT_IGN_ZEROES "ignore_zero_blocks"
#define DM_VERITY_OPT_AT_MOST_ONCE "check_at_most_once"
#define DM_VERITY_OPT_TASKLET_VERIFY "try_verify_in_tasklet"
#define DM_VERITY_OPTS_MAX (4 + DM_VERITY_OPTS_FEC + \
DM_VERITY_ROOT_HASH_VERIFICATION_OPTS)
static unsigned int dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, 0644);
static DEFINE_STATIC_KEY_FALSE(use_tasklet_enabled);
struct dm_verity_prefetch_work {
struct work_struct work;
struct dm_verity *v;
sector_t block;
unsigned int n_blocks;
};
/*
* Auxiliary structure appended to each dm-bufio buffer. If the value
* hash_verified is nonzero, hash of the block has been verified.
*
* The variable hash_verified is set to 0 when allocating the buffer, then
* it can be changed to 1 and it is never reset to 0 again.
*
* There is no lock around this value, a race condition can at worst cause
* that multiple processes verify the hash of the same buffer simultaneously
* and write 1 to hash_verified simultaneously.
* This condition is harmless, so we don't need locking.
*/
struct buffer_aux {
int hash_verified;
};
/*
* Initialize struct buffer_aux for a freshly created buffer.
*/
static void dm_bufio_alloc_callback(struct dm_buffer *buf)
{
struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
aux->hash_verified = 0;
}
/*
* Translate input sector number to the sector number on the target device.
*/
static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
{
return v->data_start + dm_target_offset(v->ti, bi_sector);
}
/*
* Return hash position of a specified block at a specified tree level
* (0 is the lowest level).
* The lowest "hash_per_block_bits"-bits of the result denote hash position
* inside a hash block. The remaining bits denote location of the hash block.
*/
static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
int level)
{
return block >> (level * v->hash_per_block_bits);
}
static int verity_hash_update(struct dm_verity *v, struct ahash_request *req,
const u8 *data, size_t len,
struct crypto_wait *wait)
{
struct scatterlist sg;
if (likely(!is_vmalloc_addr(data))) {
sg_init_one(&sg, data, len);
ahash_request_set_crypt(req, &sg, NULL, len);
return crypto_wait_req(crypto_ahash_update(req), wait);
}
do {
int r;
size_t this_step = min_t(size_t, len, PAGE_SIZE - offset_in_page(data));
flush_kernel_vmap_range((void *)data, this_step);
sg_init_table(&sg, 1);
sg_set_page(&sg, vmalloc_to_page(data), this_step, offset_in_page(data));
ahash_request_set_crypt(req, &sg, NULL, this_step);
r = crypto_wait_req(crypto_ahash_update(req), wait);
if (unlikely(r))
return r;
data += this_step;
len -= this_step;
} while (len);
return 0;
}
/*
* Wrapper for crypto_ahash_init, which handles verity salting.
*/
static int verity_hash_init(struct dm_verity *v, struct ahash_request *req,
struct crypto_wait *wait, bool may_sleep)
{
int r;
ahash_request_set_tfm(req, v->tfm);
ahash_request_set_callback(req,
may_sleep ? CRYPTO_TFM_REQ_MAY_SLEEP | CRYPTO_TFM_REQ_MAY_BACKLOG : 0,
crypto_req_done, (void *)wait);
crypto_init_wait(wait);
r = crypto_wait_req(crypto_ahash_init(req), wait);
if (unlikely(r < 0)) {
if (r != -ENOMEM)
DMERR("crypto_ahash_init failed: %d", r);
return r;
}
if (likely(v->salt_size && (v->version >= 1)))
r = verity_hash_update(v, req, v->salt, v->salt_size, wait);
return r;
}
static int verity_hash_final(struct dm_verity *v, struct ahash_request *req,
u8 *digest, struct crypto_wait *wait)
{
int r;
if (unlikely(v->salt_size && (!v->version))) {
r = verity_hash_update(v, req, v->salt, v->salt_size, wait);
if (r < 0) {
DMERR("%s failed updating salt: %d", __func__, r);
goto out;
}
}
ahash_request_set_crypt(req, NULL, digest, 0);
r = crypto_wait_req(crypto_ahash_final(req), wait);
out:
return r;
}
int verity_hash(struct dm_verity *v, struct ahash_request *req,
const u8 *data, size_t len, u8 *digest, bool may_sleep)
{
int r;
struct crypto_wait wait;
r = verity_hash_init(v, req, &wait, may_sleep);
if (unlikely(r < 0))
goto out;
r = verity_hash_update(v, req, data, len, &wait);
if (unlikely(r < 0))
goto out;
r = verity_hash_final(v, req, digest, &wait);
out:
return r;
}
static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
sector_t *hash_block, unsigned int *offset)
{
sector_t position = verity_position_at_level(v, block, level);
unsigned int idx;
*hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
if (!offset)
return;
idx = position & ((1 << v->hash_per_block_bits) - 1);
if (!v->version)
*offset = idx * v->digest_size;
else
*offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
}
/*
* Handle verification errors.
*/
static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
unsigned long long block)
{
char verity_env[DM_VERITY_ENV_LENGTH];
char *envp[] = { verity_env, NULL };
const char *type_str = "";
struct mapped_device *md = dm_table_get_md(v->ti->table);
/* Corruption should be visible in device status in all modes */
v->hash_failed = true;
if (v->corrupted_errs >= DM_VERITY_MAX_CORRUPTED_ERRS)
goto out;
v->corrupted_errs++;
switch (type) {
case DM_VERITY_BLOCK_TYPE_DATA:
type_str = "data";
break;
case DM_VERITY_BLOCK_TYPE_METADATA:
type_str = "metadata";
break;
default:
BUG();
}
DMERR_LIMIT("%s: %s block %llu is corrupted", v->data_dev->name,
type_str, block);
if (v->corrupted_errs == DM_VERITY_MAX_CORRUPTED_ERRS) {
DMERR("%s: reached maximum errors", v->data_dev->name);
dm_audit_log_target(DM_MSG_PREFIX, "max-corrupted-errors", v->ti, 0);
}
snprintf(verity_env, DM_VERITY_ENV_LENGTH, "%s=%d,%llu",
DM_VERITY_ENV_VAR_NAME, type, block);
kobject_uevent_env(&disk_to_dev(dm_disk(md))->kobj, KOBJ_CHANGE, envp);
out:
if (v->mode == DM_VERITY_MODE_LOGGING)
return 0;
if (v->mode == DM_VERITY_MODE_RESTART)
kernel_restart("dm-verity device corrupted");
if (v->mode == DM_VERITY_MODE_PANIC)
panic("dm-verity device corrupted");
return 1;
}
/*
* Verify hash of a metadata block pertaining to the specified data block
* ("block" argument) at a specified level ("level" argument).
*
* On successful return, verity_io_want_digest(v, io) contains the hash value
* for a lower tree level or for the data block (if we're at the lowest level).
*
* If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
* If "skip_unverified" is false, unverified buffer is hashed and verified
* against current value of verity_io_want_digest(v, io).
*/
static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
sector_t block, int level, bool skip_unverified,
u8 *want_digest)
{
struct dm_buffer *buf;
struct buffer_aux *aux;
u8 *data;
int r;
sector_t hash_block;
unsigned int offset;
verity_hash_at_level(v, block, level, &hash_block, &offset);
if (static_branch_unlikely(&use_tasklet_enabled) && io->in_tasklet) {
data = dm_bufio_get(v->bufio, hash_block, &buf);
if (data == NULL) {
/*
* In tasklet and the hash was not in the bufio cache.
* Return early and resume execution from a work-queue
* to read the hash from disk.
*/
return -EAGAIN;
}
} else
data = dm_bufio_read(v->bufio, hash_block, &buf);
if (IS_ERR(data))
return PTR_ERR(data);
aux = dm_bufio_get_aux_data(buf);
if (!aux->hash_verified) {
if (skip_unverified) {
r = 1;
goto release_ret_r;
}
r = verity_hash(v, verity_io_hash_req(v, io),
data, 1 << v->hash_dev_block_bits,
verity_io_real_digest(v, io), !io->in_tasklet);
if (unlikely(r < 0))
goto release_ret_r;
if (likely(memcmp(verity_io_real_digest(v, io), want_digest,
v->digest_size) == 0))
aux->hash_verified = 1;
else if (static_branch_unlikely(&use_tasklet_enabled) &&
io->in_tasklet) {
/*
* Error handling code (FEC included) cannot be run in a
* tasklet since it may sleep, so fallback to work-queue.
*/
r = -EAGAIN;
goto release_ret_r;
} else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA,
hash_block, data, NULL) == 0)
aux->hash_verified = 1;
else if (verity_handle_err(v,
DM_VERITY_BLOCK_TYPE_METADATA,
hash_block)) {
struct bio *bio =
dm_bio_from_per_bio_data(io,
v->ti->per_io_data_size);
dm_audit_log_bio(DM_MSG_PREFIX, "verify-metadata", bio,
block, 0);
r = -EIO;
goto release_ret_r;
}
}
data += offset;
memcpy(want_digest, data, v->digest_size);
r = 0;
release_ret_r:
dm_bufio_release(buf);
return r;
}
/*
* Find a hash for a given block, write it to digest and verify the integrity
* of the hash tree if necessary.
*/
int verity_hash_for_block(struct dm_verity *v, struct dm_verity_io *io,
sector_t block, u8 *digest, bool *is_zero)
{
int r = 0, i;
if (likely(v->levels)) {
/*
* First, we try to get the requested hash for
* the current block. If the hash block itself is
* verified, zero is returned. If it isn't, this
* function returns 1 and we fall back to whole
* chain verification.
*/
r = verity_verify_level(v, io, block, 0, true, digest);
if (likely(r <= 0))
goto out;
}
memcpy(digest, v->root_digest, v->digest_size);
for (i = v->levels - 1; i >= 0; i--) {
r = verity_verify_level(v, io, block, i, false, digest);
if (unlikely(r))
goto out;
}
out:
if (!r && v->zero_digest)
*is_zero = !memcmp(v->zero_digest, digest, v->digest_size);
else
*is_zero = false;
return r;
}
/*
* Calculates the digest for the given bio
*/
static int verity_for_io_block(struct dm_verity *v, struct dm_verity_io *io,
struct bvec_iter *iter, struct crypto_wait *wait)
{
unsigned int todo = 1 << v->data_dev_block_bits;
struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
struct scatterlist sg;
struct ahash_request *req = verity_io_hash_req(v, io);
do {
int r;
unsigned int len;
struct bio_vec bv = bio_iter_iovec(bio, *iter);
sg_init_table(&sg, 1);
len = bv.bv_len;
if (likely(len >= todo))
len = todo;
/*
* Operating on a single page at a time looks suboptimal
* until you consider the typical block size is 4,096B.
* Going through this loops twice should be very rare.
*/
sg_set_page(&sg, bv.bv_page, len, bv.bv_offset);
ahash_request_set_crypt(req, &sg, NULL, len);
r = crypto_wait_req(crypto_ahash_update(req), wait);
if (unlikely(r < 0)) {
DMERR("%s crypto op failed: %d", __func__, r);
return r;
}
bio_advance_iter(bio, iter, len);
todo -= len;
} while (todo);
return 0;
}
/*
* Calls function process for 1 << v->data_dev_block_bits bytes in the bio_vec
* starting from iter.
*/
int verity_for_bv_block(struct dm_verity *v, struct dm_verity_io *io,
struct bvec_iter *iter,
int (*process)(struct dm_verity *v,
struct dm_verity_io *io, u8 *data,
size_t len))
{
unsigned int todo = 1 << v->data_dev_block_bits;
struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
do {
int r;
u8 *page;
unsigned int len;
struct bio_vec bv = bio_iter_iovec(bio, *iter);
page = bvec_kmap_local(&bv);
len = bv.bv_len;
if (likely(len >= todo))
len = todo;
r = process(v, io, page, len);
kunmap_local(page);
if (r < 0)
return r;
bio_advance_iter(bio, iter, len);
todo -= len;
} while (todo);
return 0;
}
static int verity_bv_zero(struct dm_verity *v, struct dm_verity_io *io,
u8 *data, size_t len)
{
memset(data, 0, len);
return 0;
}
/*
* Moves the bio iter one data block forward.
*/
static inline void verity_bv_skip_block(struct dm_verity *v,
struct dm_verity_io *io,
struct bvec_iter *iter)
{
struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
bio_advance_iter(bio, iter, 1 << v->data_dev_block_bits);
}
/*
* Verify one "dm_verity_io" structure.
*/
static int verity_verify_io(struct dm_verity_io *io)
{
bool is_zero;
struct dm_verity *v = io->v;
#if defined(CONFIG_DM_VERITY_FEC)
struct bvec_iter start;
#endif
struct bvec_iter iter_copy;
struct bvec_iter *iter;
struct crypto_wait wait;
struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
unsigned int b;
if (static_branch_unlikely(&use_tasklet_enabled) && io->in_tasklet) {
/*
* Copy the iterator in case we need to restart
* verification in a work-queue.
*/
iter_copy = io->iter;
iter = &iter_copy;
} else
iter = &io->iter;
for (b = 0; b < io->n_blocks; b++) {
int r;
sector_t cur_block = io->block + b;
struct ahash_request *req = verity_io_hash_req(v, io);
if (v->validated_blocks && bio->bi_status == BLK_STS_OK &&
likely(test_bit(cur_block, v->validated_blocks))) {
verity_bv_skip_block(v, io, iter);
continue;
}
r = verity_hash_for_block(v, io, cur_block,
verity_io_want_digest(v, io),
&is_zero);
if (unlikely(r < 0))
return r;
if (is_zero) {
/*
* If we expect a zero block, don't validate, just
* return zeros.
*/
r = verity_for_bv_block(v, io, iter,
verity_bv_zero);
if (unlikely(r < 0))
return r;
continue;
}
r = verity_hash_init(v, req, &wait, !io->in_tasklet);
if (unlikely(r < 0))
return r;
#if defined(CONFIG_DM_VERITY_FEC)
if (verity_fec_is_enabled(v))
start = *iter;
#endif
r = verity_for_io_block(v, io, iter, &wait);
if (unlikely(r < 0))
return r;
r = verity_hash_final(v, req, verity_io_real_digest(v, io),
&wait);
if (unlikely(r < 0))
return r;
if (likely(memcmp(verity_io_real_digest(v, io),
verity_io_want_digest(v, io), v->digest_size) == 0)) {
if (v->validated_blocks)
set_bit(cur_block, v->validated_blocks);
continue;
} else if (static_branch_unlikely(&use_tasklet_enabled) &&
io->in_tasklet) {
/*
* Error handling code (FEC included) cannot be run in a
* tasklet since it may sleep, so fallback to work-queue.
*/
return -EAGAIN;
#if defined(CONFIG_DM_VERITY_FEC)
} else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA,
cur_block, NULL, &start) == 0) {
continue;
#endif
} else {
if (bio->bi_status) {
/*
* Error correction failed; Just return error
*/
return -EIO;
}
if (verity_handle_err(v, DM_VERITY_BLOCK_TYPE_DATA,
cur_block)) {
dm_audit_log_bio(DM_MSG_PREFIX, "verify-data",
bio, cur_block, 0);
return -EIO;
}
}
}
return 0;
}
/*
* Skip verity work in response to I/O error when system is shutting down.
*/
static inline bool verity_is_system_shutting_down(void)
{
return system_state == SYSTEM_HALT || system_state == SYSTEM_POWER_OFF
|| system_state == SYSTEM_RESTART;
}
/*
* End one "io" structure with a given error.
*/
static void verity_finish_io(struct dm_verity_io *io, blk_status_t status)
{
struct dm_verity *v = io->v;
struct bio *bio = dm_bio_from_per_bio_data(io, v->ti->per_io_data_size);
bio->bi_end_io = io->orig_bi_end_io;
bio->bi_status = status;
if (!static_branch_unlikely(&use_tasklet_enabled) || !io->in_tasklet)
verity_fec_finish_io(io);
bio_endio(bio);
}
static void verity_work(struct work_struct *w)
{
struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
io->in_tasklet = false;
verity_finish_io(io, errno_to_blk_status(verity_verify_io(io)));
}
static void verity_tasklet(unsigned long data)
{
struct dm_verity_io *io = (struct dm_verity_io *)data;
int err;
io->in_tasklet = true;
err = verity_verify_io(io);
if (err == -EAGAIN || err == -ENOMEM) {
/* fallback to retrying with work-queue */
INIT_WORK(&io->work, verity_work);
queue_work(io->v->verify_wq, &io->work);
return;
}
verity_finish_io(io, errno_to_blk_status(err));
}
static void verity_end_io(struct bio *bio)
{
struct dm_verity_io *io = bio->bi_private;
if (bio->bi_status &&
(!verity_fec_is_enabled(io->v) ||
verity_is_system_shutting_down() ||
(bio->bi_opf & REQ_RAHEAD))) {
verity_finish_io(io, bio->bi_status);
return;
}
if (static_branch_unlikely(&use_tasklet_enabled) && io->v->use_tasklet) {
tasklet_init(&io->tasklet, verity_tasklet, (unsigned long)io);
tasklet_schedule(&io->tasklet);
} else {
INIT_WORK(&io->work, verity_work);
queue_work(io->v->verify_wq, &io->work);
}
}
/*
* Prefetch buffers for the specified io.
* The root buffer is not prefetched, it is assumed that it will be cached
* all the time.
*/
static void verity_prefetch_io(struct work_struct *work)
{
struct dm_verity_prefetch_work *pw =
container_of(work, struct dm_verity_prefetch_work, work);
struct dm_verity *v = pw->v;
int i;
for (i = v->levels - 2; i >= 0; i--) {
sector_t hash_block_start;
sector_t hash_block_end;
verity_hash_at_level(v, pw->block, i, &hash_block_start, NULL);
verity_hash_at_level(v, pw->block + pw->n_blocks - 1, i, &hash_block_end, NULL);
if (!i) {
unsigned int cluster = READ_ONCE(dm_verity_prefetch_cluster);
cluster >>= v->data_dev_block_bits;
if (unlikely(!cluster))
goto no_prefetch_cluster;
if (unlikely(cluster & (cluster - 1)))
cluster = 1 << __fls(cluster);
hash_block_start &= ~(sector_t)(cluster - 1);
hash_block_end |= cluster - 1;
if (unlikely(hash_block_end >= v->hash_blocks))
hash_block_end = v->hash_blocks - 1;
}
no_prefetch_cluster:
dm_bufio_prefetch(v->bufio, hash_block_start,
hash_block_end - hash_block_start + 1);
}
kfree(pw);
}
static void verity_submit_prefetch(struct dm_verity *v, struct dm_verity_io *io)
{
sector_t block = io->block;
unsigned int n_blocks = io->n_blocks;
struct dm_verity_prefetch_work *pw;
if (v->validated_blocks) {
while (n_blocks && test_bit(block, v->validated_blocks)) {
block++;
n_blocks--;
}
while (n_blocks && test_bit(block + n_blocks - 1,
v->validated_blocks))
n_blocks--;
if (!n_blocks)
return;
}
pw = kmalloc(sizeof(struct dm_verity_prefetch_work),
GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
if (!pw)
return;
INIT_WORK(&pw->work, verity_prefetch_io);
pw->v = v;
pw->block = block;
pw->n_blocks = n_blocks;
queue_work(v->verify_wq, &pw->work);
}
/*
* Bio map function. It allocates dm_verity_io structure and bio vector and
* fills them. Then it issues prefetches and the I/O.
*/
static int verity_map(struct dm_target *ti, struct bio *bio)
{
struct dm_verity *v = ti->private;
struct dm_verity_io *io;
bio_set_dev(bio, v->data_dev->bdev);
bio->bi_iter.bi_sector = verity_map_sector(v, bio->bi_iter.bi_sector);
if (((unsigned int)bio->bi_iter.bi_sector | bio_sectors(bio)) &
((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
DMERR_LIMIT("unaligned io");
return DM_MAPIO_KILL;
}
if (bio_end_sector(bio) >>
(v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
DMERR_LIMIT("io out of range");
return DM_MAPIO_KILL;
}
if (bio_data_dir(bio) == WRITE)
return DM_MAPIO_KILL;
io = dm_per_bio_data(bio, ti->per_io_data_size);
io->v = v;
io->orig_bi_end_io = bio->bi_end_io;
io->block = bio->bi_iter.bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
io->n_blocks = bio->bi_iter.bi_size >> v->data_dev_block_bits;
bio->bi_end_io = verity_end_io;
bio->bi_private = io;
io->iter = bio->bi_iter;
verity_fec_init_io(io);
verity_submit_prefetch(v, io);
submit_bio_noacct(bio);
return DM_MAPIO_SUBMITTED;
}
/*
* Status: V (valid) or C (corruption found)
*/
static void verity_status(struct dm_target *ti, status_type_t type,
unsigned int status_flags, char *result, unsigned int maxlen)
{
struct dm_verity *v = ti->private;
unsigned int args = 0;
unsigned int sz = 0;
unsigned int x;
switch (type) {
case STATUSTYPE_INFO:
DMEMIT("%c", v->hash_failed ? 'C' : 'V');
break;
case STATUSTYPE_TABLE:
DMEMIT("%u %s %s %u %u %llu %llu %s ",
v->version,
v->data_dev->name,
v->hash_dev->name,
1 << v->data_dev_block_bits,
1 << v->hash_dev_block_bits,
(unsigned long long)v->data_blocks,
(unsigned long long)v->hash_start,
v->alg_name
);
for (x = 0; x < v->digest_size; x++)
DMEMIT("%02x", v->root_digest[x]);
DMEMIT(" ");
if (!v->salt_size)
DMEMIT("-");
else
for (x = 0; x < v->salt_size; x++)
DMEMIT("%02x", v->salt[x]);
if (v->mode != DM_VERITY_MODE_EIO)
args++;
if (verity_fec_is_enabled(v))
args += DM_VERITY_OPTS_FEC;
if (v->zero_digest)
args++;
if (v->validated_blocks)
args++;
if (v->use_tasklet)
args++;
if (v->signature_key_desc)
args += DM_VERITY_ROOT_HASH_VERIFICATION_OPTS;
if (!args)
return;
DMEMIT(" %u", args);
if (v->mode != DM_VERITY_MODE_EIO) {
DMEMIT(" ");
switch (v->mode) {
case DM_VERITY_MODE_LOGGING:
DMEMIT(DM_VERITY_OPT_LOGGING);
break;
case DM_VERITY_MODE_RESTART:
DMEMIT(DM_VERITY_OPT_RESTART);
break;
case DM_VERITY_MODE_PANIC:
DMEMIT(DM_VERITY_OPT_PANIC);
break;
default:
BUG();
}
}
if (v->zero_digest)
DMEMIT(" " DM_VERITY_OPT_IGN_ZEROES);
if (v->validated_blocks)
DMEMIT(" " DM_VERITY_OPT_AT_MOST_ONCE);
if (v->use_tasklet)
DMEMIT(" " DM_VERITY_OPT_TASKLET_VERIFY);
sz = verity_fec_status_table(v, sz, result, maxlen);
if (v->signature_key_desc)
DMEMIT(" " DM_VERITY_ROOT_HASH_VERIFICATION_OPT_SIG_KEY
" %s", v->signature_key_desc);
break;
case STATUSTYPE_IMA:
DMEMIT_TARGET_NAME_VERSION(ti->type);
DMEMIT(",hash_failed=%c", v->hash_failed ? 'C' : 'V');
DMEMIT(",verity_version=%u", v->version);
DMEMIT(",data_device_name=%s", v->data_dev->name);
DMEMIT(",hash_device_name=%s", v->hash_dev->name);
DMEMIT(",verity_algorithm=%s", v->alg_name);
DMEMIT(",root_digest=");
for (x = 0; x < v->digest_size; x++)
DMEMIT("%02x", v->root_digest[x]);
DMEMIT(",salt=");
if (!v->salt_size)
DMEMIT("-");
else
for (x = 0; x < v->salt_size; x++)
DMEMIT("%02x", v->salt[x]);
DMEMIT(",ignore_zero_blocks=%c", v->zero_digest ? 'y' : 'n');
DMEMIT(",check_at_most_once=%c", v->validated_blocks ? 'y' : 'n');
if (v->signature_key_desc)
DMEMIT(",root_hash_sig_key_desc=%s", v->signature_key_desc);
if (v->mode != DM_VERITY_MODE_EIO) {
DMEMIT(",verity_mode=");
switch (v->mode) {
case DM_VERITY_MODE_LOGGING:
DMEMIT(DM_VERITY_OPT_LOGGING);
break;
case DM_VERITY_MODE_RESTART:
DMEMIT(DM_VERITY_OPT_RESTART);
break;
case DM_VERITY_MODE_PANIC:
DMEMIT(DM_VERITY_OPT_PANIC);
break;
default:
DMEMIT("invalid");
}
}
DMEMIT(";");
break;
}
}
static int verity_prepare_ioctl(struct dm_target *ti, struct block_device **bdev)
{
struct dm_verity *v = ti->private;
*bdev = v->data_dev->bdev;
if (v->data_start || ti->len != bdev_nr_sectors(v->data_dev->bdev))
return 1;
return 0;
}
static int verity_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data)
{
struct dm_verity *v = ti->private;
return fn(ti, v->data_dev, v->data_start, ti->len, data);
}
static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
struct dm_verity *v = ti->private;
if (limits->logical_block_size < 1 << v->data_dev_block_bits)
limits->logical_block_size = 1 << v->data_dev_block_bits;
if (limits->physical_block_size < 1 << v->data_dev_block_bits)
limits->physical_block_size = 1 << v->data_dev_block_bits;
blk_limits_io_min(limits, limits->logical_block_size);
}
static void verity_dtr(struct dm_target *ti)
{
struct dm_verity *v = ti->private;
if (v->verify_wq)
destroy_workqueue(v->verify_wq);
if (v->bufio)
dm_bufio_client_destroy(v->bufio);
kvfree(v->validated_blocks);
kfree(v->salt);
kfree(v->root_digest);
kfree(v->zero_digest);
if (v->tfm)
crypto_free_ahash(v->tfm);
kfree(v->alg_name);
if (v->hash_dev)
dm_put_device(ti, v->hash_dev);
if (v->data_dev)
dm_put_device(ti, v->data_dev);
verity_fec_dtr(v);
kfree(v->signature_key_desc);
if (v->use_tasklet)
static_branch_dec(&use_tasklet_enabled);
kfree(v);
dm_audit_log_dtr(DM_MSG_PREFIX, ti, 1);
}
static int verity_alloc_most_once(struct dm_verity *v)
{
struct dm_target *ti = v->ti;
/* the bitset can only handle INT_MAX blocks */
if (v->data_blocks > INT_MAX) {
ti->error = "device too large to use check_at_most_once";
return -E2BIG;
}
v->validated_blocks = kvcalloc(BITS_TO_LONGS(v->data_blocks),
sizeof(unsigned long),
GFP_KERNEL);
if (!v->validated_blocks) {
ti->error = "failed to allocate bitset for check_at_most_once";
return -ENOMEM;
}
return 0;
}
static int verity_alloc_zero_digest(struct dm_verity *v)
{
int r = -ENOMEM;
struct ahash_request *req;
u8 *zero_data;
v->zero_digest = kmalloc(v->digest_size, GFP_KERNEL);
if (!v->zero_digest)
return r;
req = kmalloc(v->ahash_reqsize, GFP_KERNEL);
if (!req)
return r; /* verity_dtr will free zero_digest */
zero_data = kzalloc(1 << v->data_dev_block_bits, GFP_KERNEL);
if (!zero_data)
goto out;
r = verity_hash(v, req, zero_data, 1 << v->data_dev_block_bits,
v->zero_digest, true);
out:
kfree(req);
kfree(zero_data);
return r;
}
static inline bool verity_is_verity_mode(const char *arg_name)
{
return (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING) ||
!strcasecmp(arg_name, DM_VERITY_OPT_RESTART) ||
!strcasecmp(arg_name, DM_VERITY_OPT_PANIC));
}
static int verity_parse_verity_mode(struct dm_verity *v, const char *arg_name)
{
if (v->mode)
return -EINVAL;
if (!strcasecmp(arg_name, DM_VERITY_OPT_LOGGING))
v->mode = DM_VERITY_MODE_LOGGING;
else if (!strcasecmp(arg_name, DM_VERITY_OPT_RESTART))
v->mode = DM_VERITY_MODE_RESTART;
else if (!strcasecmp(arg_name, DM_VERITY_OPT_PANIC))
v->mode = DM_VERITY_MODE_PANIC;
return 0;
}
static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
struct dm_verity_sig_opts *verify_args,
bool only_modifier_opts)
{
int r = 0;
unsigned int argc;
struct dm_target *ti = v->ti;
const char *arg_name;
static const struct dm_arg _args[] = {
{0, DM_VERITY_OPTS_MAX, "Invalid number of feature args"},
};
r = dm_read_arg_group(_args, as, &argc, &ti->error);
if (r)
return -EINVAL;
if (!argc)
return 0;
do {
arg_name = dm_shift_arg(as);
argc--;
if (verity_is_verity_mode(arg_name)) {
if (only_modifier_opts)
continue;
r = verity_parse_verity_mode(v, arg_name);
if (r) {
ti->error = "Conflicting error handling parameters";
return r;
}
continue;
} else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROES)) {
if (only_modifier_opts)
continue;
r = verity_alloc_zero_digest(v);
if (r) {
ti->error = "Cannot allocate zero digest";
return r;
}
continue;
} else if (!strcasecmp(arg_name, DM_VERITY_OPT_AT_MOST_ONCE)) {
if (only_modifier_opts)
continue;
r = verity_alloc_most_once(v);
if (r)
return r;
continue;
} else if (!strcasecmp(arg_name, DM_VERITY_OPT_TASKLET_VERIFY)) {
v->use_tasklet = true;
static_branch_inc(&use_tasklet_enabled);
continue;
} else if (verity_is_fec_opt_arg(arg_name)) {
if (only_modifier_opts)
continue;
r = verity_fec_parse_opt_args(as, v, &argc, arg_name);
if (r)
return r;
continue;
} else if (verity_verify_is_sig_opt_arg(arg_name)) {
if (only_modifier_opts)
continue;
r = verity_verify_sig_parse_opt_args(as, v,
verify_args,
&argc, arg_name);
if (r)
return r;
continue;
} else if (only_modifier_opts) {
/*
* Ignore unrecognized opt, could easily be an extra
* argument to an option whose parsing was skipped.
* Normal parsing (@only_modifier_opts=false) will
* properly parse all options (and their extra args).
*/
continue;
}
DMERR("Unrecognized verity feature request: %s", arg_name);
ti->error = "Unrecognized verity feature request";
return -EINVAL;
} while (argc && !r);
return r;
}
/*
* Target parameters:
* <version> The current format is version 1.
* Vsn 0 is compatible with original Chromium OS releases.
* <data device>
* <hash device>
* <data block size>
* <hash block size>
* <the number of data blocks>
* <hash start block>
* <algorithm>
* <digest>
* <salt> Hex string or "-" if no salt.
*/
static int verity_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct dm_verity *v;
struct dm_verity_sig_opts verify_args = {0};
struct dm_arg_set as;
unsigned int num;
unsigned long long num_ll;
int r;
int i;
sector_t hash_position;
char dummy;
char *root_hash_digest_to_validate;
v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
if (!v) {
ti->error = "Cannot allocate verity structure";
return -ENOMEM;
}
ti->private = v;
v->ti = ti;
r = verity_fec_ctr_alloc(v);
if (r)
goto bad;
if ((dm_table_get_mode(ti->table) & ~BLK_OPEN_READ)) {
ti->error = "Device must be readonly";
r = -EINVAL;
goto bad;
}
if (argc < 10) {
ti->error = "Not enough arguments";
r = -EINVAL;
goto bad;
}
/* Parse optional parameters that modify primary args */
if (argc > 10) {
as.argc = argc - 10;
as.argv = argv + 10;
r = verity_parse_opt_args(&as, v, &verify_args, true);
if (r < 0)
goto bad;
}
if (sscanf(argv[0], "%u%c", &num, &dummy) != 1 ||
num > 1) {
ti->error = "Invalid version";
r = -EINVAL;
goto bad;
}
v->version = num;
r = dm_get_device(ti, argv[1], BLK_OPEN_READ, &v->data_dev);
if (r) {
ti->error = "Data device lookup failed";
goto bad;
}
r = dm_get_device(ti, argv[2], BLK_OPEN_READ, &v->hash_dev);
if (r) {
ti->error = "Hash device lookup failed";
goto bad;
}
if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
!num || (num & (num - 1)) ||
num < bdev_logical_block_size(v->data_dev->bdev) ||
num > PAGE_SIZE) {
ti->error = "Invalid data device block size";
r = -EINVAL;
goto bad;
}
v->data_dev_block_bits = __ffs(num);
if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
!num || (num & (num - 1)) ||
num < bdev_logical_block_size(v->hash_dev->bdev) ||
num > INT_MAX) {
ti->error = "Invalid hash device block size";
r = -EINVAL;
goto bad;
}
v->hash_dev_block_bits = __ffs(num);
if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
(sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
>> (v->data_dev_block_bits - SECTOR_SHIFT) != num_ll) {
ti->error = "Invalid data blocks";
r = -EINVAL;
goto bad;
}
v->data_blocks = num_ll;
if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
ti->error = "Data device is too small";
r = -EINVAL;
goto bad;
}
if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
(sector_t)(num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT))
>> (v->hash_dev_block_bits - SECTOR_SHIFT) != num_ll) {
ti->error = "Invalid hash start";
r = -EINVAL;
goto bad;
}
v->hash_start = num_ll;
v->alg_name = kstrdup(argv[7], GFP_KERNEL);
if (!v->alg_name) {
ti->error = "Cannot allocate algorithm name";
r = -ENOMEM;
goto bad;
}
v->tfm = crypto_alloc_ahash(v->alg_name, 0,
v->use_tasklet ? CRYPTO_ALG_ASYNC : 0);
if (IS_ERR(v->tfm)) {
ti->error = "Cannot initialize hash function";
r = PTR_ERR(v->tfm);
v->tfm = NULL;
goto bad;
}
/*
* dm-verity performance can vary greatly depending on which hash
* algorithm implementation is used. Help people debug performance
* problems by logging the ->cra_driver_name.
*/
DMINFO("%s using implementation \"%s\"", v->alg_name,
crypto_hash_alg_common(v->tfm)->base.cra_driver_name);
v->digest_size = crypto_ahash_digestsize(v->tfm);
if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
ti->error = "Digest size too big";
r = -EINVAL;
goto bad;
}
v->ahash_reqsize = sizeof(struct ahash_request) +
crypto_ahash_reqsize(v->tfm);
v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
if (!v->root_digest) {
ti->error = "Cannot allocate root digest";
r = -ENOMEM;
goto bad;
}
if (strlen(argv[8]) != v->digest_size * 2 ||
hex2bin(v->root_digest, argv[8], v->digest_size)) {
ti->error = "Invalid root digest";
r = -EINVAL;
goto bad;
}
root_hash_digest_to_validate = argv[8];
if (strcmp(argv[9], "-")) {
v->salt_size = strlen(argv[9]) / 2;
v->salt = kmalloc(v->salt_size, GFP_KERNEL);
if (!v->salt) {
ti->error = "Cannot allocate salt";
r = -ENOMEM;
goto bad;
}
if (strlen(argv[9]) != v->salt_size * 2 ||
hex2bin(v->salt, argv[9], v->salt_size)) {
ti->error = "Invalid salt";
r = -EINVAL;
goto bad;
}
}
argv += 10;
argc -= 10;
/* Optional parameters */
if (argc) {
as.argc = argc;
as.argv = argv;
r = verity_parse_opt_args(&as, v, &verify_args, false);
if (r < 0)
goto bad;
}
/* Root hash signature is a optional parameter*/
r = verity_verify_root_hash(root_hash_digest_to_validate,
strlen(root_hash_digest_to_validate),
verify_args.sig,
verify_args.sig_size);
if (r < 0) {
ti->error = "Root hash verification failed";
goto bad;
}
v->hash_per_block_bits =
__fls((1 << v->hash_dev_block_bits) / v->digest_size);
v->levels = 0;
if (v->data_blocks)
while (v->hash_per_block_bits * v->levels < 64 &&
(unsigned long long)(v->data_blocks - 1) >>
(v->hash_per_block_bits * v->levels))
v->levels++;
if (v->levels > DM_VERITY_MAX_LEVELS) {
ti->error = "Too many tree levels";
r = -E2BIG;
goto bad;
}
hash_position = v->hash_start;
for (i = v->levels - 1; i >= 0; i--) {
sector_t s;
v->hash_level_block[i] = hash_position;
s = (v->data_blocks + ((sector_t)1 << ((i + 1) * v->hash_per_block_bits)) - 1)
>> ((i + 1) * v->hash_per_block_bits);
if (hash_position + s < hash_position) {
ti->error = "Hash device offset overflow";
r = -E2BIG;
goto bad;
}
hash_position += s;
}
v->hash_blocks = hash_position;
v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
dm_bufio_alloc_callback, NULL,
v->use_tasklet ? DM_BUFIO_CLIENT_NO_SLEEP : 0);
if (IS_ERR(v->bufio)) {
ti->error = "Cannot initialize dm-bufio";
r = PTR_ERR(v->bufio);
v->bufio = NULL;
goto bad;
}
if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
ti->error = "Hash device is too small";
r = -E2BIG;
goto bad;
}
/*
* Using WQ_HIGHPRI improves throughput and completion latency by
* reducing wait times when reading from a dm-verity device.
*
* Also as required for the "try_verify_in_tasklet" feature: WQ_HIGHPRI
* allows verify_wq to preempt softirq since verification in tasklet
* will fall-back to using it for error handling (or if the bufio cache
* doesn't have required hashes).
*/
v->verify_wq = alloc_workqueue("kverityd", WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
if (!v->verify_wq) {
ti->error = "Cannot allocate workqueue";
r = -ENOMEM;
goto bad;
}
ti->per_io_data_size = sizeof(struct dm_verity_io) +
v->ahash_reqsize + v->digest_size * 2;
r = verity_fec_ctr(v);
if (r)
goto bad;
ti->per_io_data_size = roundup(ti->per_io_data_size,
__alignof__(struct dm_verity_io));
verity_verify_sig_opts_cleanup(&verify_args);
dm_audit_log_ctr(DM_MSG_PREFIX, ti, 1);
return 0;
bad:
verity_verify_sig_opts_cleanup(&verify_args);
dm_audit_log_ctr(DM_MSG_PREFIX, ti, 0);
verity_dtr(ti);
return r;
}
/*
* Check whether a DM target is a verity target.
*/
bool dm_is_verity_target(struct dm_target *ti)
{
return ti->type->module == THIS_MODULE;
}
/*
* Get the verity mode (error behavior) of a verity target.
*
* Returns the verity mode of the target, or -EINVAL if 'ti' is not a verity
* target.
*/
int dm_verity_get_mode(struct dm_target *ti)
{
struct dm_verity *v = ti->private;
if (!dm_is_verity_target(ti))
return -EINVAL;
return v->mode;
}
/*
* Get the root digest of a verity target.
*
* Returns a copy of the root digest, the caller is responsible for
* freeing the memory of the digest.
*/
int dm_verity_get_root_digest(struct dm_target *ti, u8 **root_digest, unsigned int *digest_size)
{
struct dm_verity *v = ti->private;
if (!dm_is_verity_target(ti))
return -EINVAL;
*root_digest = kmemdup(v->root_digest, v->digest_size, GFP_KERNEL);
if (*root_digest == NULL)
return -ENOMEM;
*digest_size = v->digest_size;
return 0;
}
static struct target_type verity_target = {
.name = "verity",
.features = DM_TARGET_IMMUTABLE,
.version = {1, 9, 0},
.module = THIS_MODULE,
.ctr = verity_ctr,
.dtr = verity_dtr,
.map = verity_map,
.status = verity_status,
.prepare_ioctl = verity_prepare_ioctl,
.iterate_devices = verity_iterate_devices,
.io_hints = verity_io_hints,
};
module_dm(verity);
MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
MODULE_LICENSE("GPL");