If a userspace process reads (with O_DIRECT) multiple blocks into the same buffer, dm-verity reports an error [1]. This commit fixes dm-verity, so that if hash verification fails, the data is read again into a kernel buffer (where userspace can't modify it) and the hash is rechecked. If the recheck succeeds, the content of the kernel buffer is copied into the user buffer; if the recheck fails, an error is reported. [1] https://people.redhat.com/~mpatocka/testcases/blk-auth-modify/read2.c Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- drivers/md/dm-verity-target.c | 87 ++++++++++++++++++++++++++++++++++++++---- drivers/md/dm-verity.h | 6 ++ 2 files changed, 86 insertions(+), 7 deletions(-) Index: linux-2.6/drivers/md/dm-verity-target.c =================================================================== --- linux-2.6.orig/drivers/md/dm-verity-target.c 2024-02-19 17:22:37.000000000 +0100 +++ linux-2.6/drivers/md/dm-verity-target.c 2024-02-19 17:24:04.000000000 +0100 @@ -482,6 +482,62 @@ int verity_for_bv_block(struct dm_verity return 0; } +static int verity_recheck_copy(struct dm_verity *v, struct dm_verity_io *io, + u8 *data, size_t len) +{ + memcpy(data, io->recheck_buffer, len); + io->recheck_buffer += len; + + return 0; +} + +static int verity_recheck(struct dm_verity *v, struct dm_verity_io *io, + struct bvec_iter start, sector_t cur_block) +{ + struct page *page; + void *buffer; + int r; + struct dm_io_request io_req; + struct dm_io_region io_loc; + + page = mempool_alloc(&v->recheck_pool, GFP_NOIO); + buffer = page_to_virt(page); + + io_req.bi_opf = REQ_OP_READ; + io_req.mem.type = DM_IO_KMEM; + io_req.mem.ptr.addr = buffer; + io_req.notify.fn = NULL; + io_req.client = v->io; + io_loc.bdev = v->data_dev->bdev; + io_loc.sector = cur_block << (v->data_dev_block_bits - SECTOR_SHIFT); + io_loc.count = 1 << (v->data_dev_block_bits - SECTOR_SHIFT); + r = dm_io(&io_req, 1, &io_loc, NULL); + if (unlikely(r)) + goto free_ret; + + r = verity_hash(v, verity_io_hash_req(v, io), buffer, 1 << v->data_dev_block_bits, + verity_io_real_digest(v, io), true); + + if (unlikely(r)) + goto free_ret; + + if (memcmp(verity_io_real_digest(v, io), verity_io_want_digest(v, io), v->digest_size)) { + r = -EIO; + goto free_ret; + } + + io->recheck_buffer = buffer; + r = verity_for_bv_block(v, io, &start, verity_recheck_copy); + if (unlikely(r)) + goto free_ret; + + r = 0; +free_ret: + mempool_free(page, &v->recheck_pool); + + return r; +} + static int verity_bv_zero(struct dm_verity *v, struct dm_verity_io *io, u8 *data, size_t len) { @@ -508,9 +564,7 @@ static int verity_verify_io(struct dm_ve { 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; @@ -561,10 +615,7 @@ static int verity_verify_io(struct dm_ve if (unlikely(r < 0)) return r; -#if defined(CONFIG_DM_VERITY_FEC) - if (verity_fec_is_enabled(v)) - start = *iter; -#endif + start = *iter; r = verity_for_io_block(v, io, iter, &wait); if (unlikely(r < 0)) return r; @@ -586,6 +637,10 @@ static int verity_verify_io(struct dm_ve * tasklet since it may sleep, so fallback to work-queue. */ return -EAGAIN; + } else if (verity_recheck(v, io, start, cur_block) == 0) { + if (v->validated_blocks) + set_bit(cur_block, v->validated_blocks); + continue; #if defined(CONFIG_DM_VERITY_FEC) } else if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_DATA, cur_block, NULL, &start) == 0) { @@ -941,6 +996,10 @@ static void verity_dtr(struct dm_target if (v->verify_wq) destroy_workqueue(v->verify_wq); + mempool_exit(&v->recheck_pool); + if (v->io) + dm_io_client_destroy(v->io); + if (v->bufio) dm_bufio_client_destroy(v->bufio); @@ -1379,6 +1438,20 @@ static int verity_ctr(struct dm_target * } v->hash_blocks = hash_position; + r = mempool_init_page_pool(&v->recheck_pool, 1, 0); + if (unlikely(r)) { + ti->error = "Cannot allocate mempool"; + goto bad; + } + + v->io = dm_io_client_create(); + if (IS_ERR(v->io)) { + r = PTR_ERR(v->io); + v->io = NULL; + ti->error = "Cannot allocate dm io"; + goto bad; + } + 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, @@ -1486,7 +1559,7 @@ int dm_verity_get_root_digest(struct dm_ static struct target_type verity_target = { .name = "verity", .features = DM_TARGET_IMMUTABLE, - .version = {1, 9, 0}, + .version = {1, 10, 0}, .module = THIS_MODULE, .ctr = verity_ctr, .dtr = verity_dtr, Index: linux-2.6/drivers/md/dm-verity.h =================================================================== --- linux-2.6.orig/drivers/md/dm-verity.h 2024-02-19 17:22:37.000000000 +0100 +++ linux-2.6/drivers/md/dm-verity.h 2024-02-19 17:22:37.000000000 +0100 @@ -11,6 +11,7 @@ #ifndef DM_VERITY_H #define DM_VERITY_H +#include <linux/dm-io.h> #include <linux/dm-bufio.h> #include <linux/device-mapper.h> #include <linux/interrupt.h> @@ -68,6 +69,9 @@ struct dm_verity { unsigned long *validated_blocks; /* bitset blocks validated */ char *signature_key_desc; /* signature keyring reference */ + + struct dm_io_client *io; + mempool_t recheck_pool; }; struct dm_verity_io { @@ -84,6 +88,8 @@ struct dm_verity_io { struct work_struct work; + char *recheck_buffer; + /* * Three variably-size fields follow this struct: *
