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Subject[PATCH] dm: verity support data device offset
Date
I needed to add support for dm-verity with data that is offset into a block device. As part of this I found that the existing code did not compute the correct hash block index if the data_start might be non-zero. Here's a patch to add support for a data offset target parameter as well as a fix to the hash block index computation.

Patch and (hopefully proper) commit message below. Thanks.
--
Wesley Miaw

============================================================

Add data device start block index to dm-verity target parameters to support verity targets where the data does not begin at sector 0 of the block device. Also fix the hash block index computation so it takes into account data offsets.

---

--- a/drivers/md/dm-verity.c 2012-08-07 16:03:03.778759000 -0700
+++ b/drivers/md/dm-verity.c 2012-08-07 17:30:56.914569414 -0700
@@ -491,7 +491,7 @@
io->bio = bio;
io->orig_bi_end_io = bio->bi_end_io;
io->orig_bi_private = bio->bi_private;
- io->block = bio->bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
+ io->block = (bio->bi_sector - v->data_start) >> (v->data_dev_block_bits - SECTOR_SHIFT);
io->n_blocks = bio->bi_size >> v->data_dev_block_bits;

bio->bi_end_io = verity_end_io;
@@ -641,6 +641,7 @@
* <hash device>
* <data block size>
* <hash block size>
+ * <data start block>
* <the number of data blocks>
* <hash start block>
* <algorithm>
@@ -671,8 +672,8 @@
goto bad;
}

- if (argc != 10) {
- ti->error = "Invalid argument count: exactly 10 arguments required";
+ if (argc != 11) {
+ ti->error = "Invalid argument count: exactly 11 arguments required";
r = -EINVAL;
goto bad;
}
@@ -718,6 +719,15 @@
v->hash_dev_block_bits = ffs(num) - 1;

if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
+ num_ll << (v->data_dev_block_bits - SECTOR_SHIFT) !=
+ (sector_t)num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) {
+ ti->error = "Invalid data start";
+ r = -EINVAL;
+ goto bad;
+ }
+ v->data_start = num_ll << (v->data_dev_block_bits - SECTOR_SHIFT);
+
+ if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
num_ll << (v->data_dev_block_bits - SECTOR_SHIFT) !=
(sector_t)num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) {
ti->error = "Invalid data blocks";
@@ -732,7 +742,7 @@
goto bad;
}

- if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
+ if (sscanf(argv[7], "%llu%c", &num_ll, &dummy) != 1 ||
num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT) !=
(sector_t)num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT)) {
ti->error = "Invalid hash start";
@@ -741,7 +751,7 @@
}
v->hash_start = num_ll;

- v->alg_name = kstrdup(argv[7], GFP_KERNEL);
+ v->alg_name = kstrdup(argv[8], GFP_KERNEL);
if (!v->alg_name) {
ti->error = "Cannot allocate algorithm name";
r = -ENOMEM;
@@ -770,23 +780,23 @@
r = -ENOMEM;
goto bad;
}
- if (strlen(argv[8]) != v->digest_size * 2 ||
- hex2bin(v->root_digest, argv[8], v->digest_size)) {
+ if (strlen(argv[9]) != v->digest_size * 2 ||
+ hex2bin(v->root_digest, argv[9], v->digest_size)) {
ti->error = "Invalid root digest";
r = -EINVAL;
goto bad;
}

- if (strcmp(argv[9], "-")) {
- v->salt_size = strlen(argv[9]) / 2;
+ if (strcmp(argv[10], "-")) {
+ v->salt_size = strlen(argv[10]) / 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)) {
+ if (strlen(argv[10]) != v->salt_size * 2 ||
+ hex2bin(v->salt, argv[10], v->salt_size)) {
ti->error = "Invalid salt";
r = -EINVAL;
goto bad;
[unhandled content-type:application/pgp-signature]
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