[PATCH] dm: verity support data device offset

[PATCH] dm: verity support data device offset

[Wesley Miaw]

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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;


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Re: [PATCH] dm: verity support data device offset

[Greg KH]

On Wed, Aug 08, 2012 at 12:43:28AM +0000, Wesley Miaw wrote:
> 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.

You forgot a "Signed-off-by:" line in the patch description here.  Take
a look at the kernel file, Documentation/SubmittingPatches for what this
means, and how to properly format the patch so it can be applied.

Also try to send the patch to the correct people who can review, and
(hopefully) apply it.  The tool, scripts/get_maintainer.pl can help you
out with that (hint, you didn't send it to anyone who could do anything
about it.)

Hope this helps,

greg k-h