Re: [PATCH v2] dm-verity: do forward error correction on metadata I/O errors

Re: [PATCH v2] dm-verity: do forward error correction on metadata I/O errors

[Mikulas Patocka]

On Mon, 10 Feb 2025, Milan Broz wrote:

> On 2/10/25 4:04 PM, Mikulas Patocka wrote:
> > Do forward error correction if metadata I/O fails.
> > 
> > Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> 
> Not directly related to this patch, but...
> please could you also increase the dm-verity version?
> 
> I just implemented support for the errors-as-corruption
> dm-verity flags in veritysetup.
> 
> The version of dm-verity stayed at 1.10 for a very long, and
> the IO error processing change was a functional change that we
> would like to detect.
> We cannot set version retrospectively, but at least now with other
> changes.
> 
> (Veritysetup tries the requested flags; if activation fails,
> it displays a better error message based on the detected
> target version. That way it works even with backports.)
> 
> Thanks,
> Milan

OK.


From: Mikulas Patocka <mpatocka@redhat.com>

Do forward error correction if metadata I/O fails.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 drivers/md/dm-verity-target.c |   21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

Index: linux-2.6/drivers/md/dm-verity-target.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-verity-target.c	2025-02-10 16:24:56.000000000 +0100
+++ linux-2.6/drivers/md/dm-verity-target.c	2025-02-10 17:43:50.000000000 +0100
@@ -324,8 +324,22 @@ static int verity_verify_level(struct dm
 						&buf, bio->bi_ioprio);
 	}
 
-	if (IS_ERR(data))
-		return PTR_ERR(data);
+	if (IS_ERR(data)) {
+		r = PTR_ERR(data);
+		data = dm_bufio_new(v->bufio, hash_block, &buf);
+		if (IS_ERR(data))
+			return r;
+		if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA,
+				      hash_block, data) == 0) {
+			aux = dm_bufio_get_aux_data(buf);
+			aux->hash_verified = 1;
+			goto release_ok;
+		} else {
+			dm_bufio_release(buf);
+			dm_bufio_forget(v->bufio, hash_block);
+			return r;
+		}
+	}
 
 	aux = dm_bufio_get_aux_data(buf);
 
@@ -366,6 +380,7 @@ static int verity_verify_level(struct dm
 		}
 	}
 
+release_ok:
 	data += offset;
 	memcpy(want_digest, data, v->digest_size);
 	r = 0;
@@ -1761,7 +1776,7 @@ static struct target_type verity_target
 	.name		= "verity",
 /* Note: the LSMs depend on the singleton and immutable features */
 	.features	= DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
-	.version	= {1, 10, 0},
+	.version	= {1, 11, 0},
 	.module		= THIS_MODULE,
 	.ctr		= verity_ctr,
 	.dtr		= verity_dtr,

[PATCH v2] dm-verity: do forward error correction on metadata I/O errors

[Mikulas Patocka]

dm-verity: do forward error correction on metadata I/O errors

Do forward error correction if metadata I/O fails.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 drivers/md/dm-verity-target.c |   25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

Index: linux-2.6/drivers/md/dm-verity-target.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-verity-target.c	2025-02-10 16:24:56.000000000 +0100
+++ linux-2.6/drivers/md/dm-verity-target.c	2025-02-17 16:47:37.000000000 +0100
@@ -311,7 +311,7 @@ static int verity_verify_level(struct dm
 
 	if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
 		data = dm_bufio_get(v->bufio, hash_block, &buf);
-		if (data == NULL) {
+		if (IS_ERR_OR_NULL(data)) {
 			/*
 			 * In tasklet and the hash was not in the bufio cache.
 			 * Return early and resume execution from a work-queue
@@ -324,8 +324,24 @@ static int verity_verify_level(struct dm
 						&buf, bio->bi_ioprio);
 	}
 
-	if (IS_ERR(data))
-		return PTR_ERR(data);
+	if (IS_ERR(data)) {
+		if (skip_unverified)
+			return 1;
+		r = PTR_ERR(data);
+		data = dm_bufio_new(v->bufio, hash_block, &buf);
+		if (IS_ERR(data))
+			return r;
+		if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA,
+				      hash_block, data) == 0) {
+			aux = dm_bufio_get_aux_data(buf);
+			aux->hash_verified = 1;
+			goto release_ok;
+		} else {
+			dm_bufio_release(buf);
+			dm_bufio_forget(v->bufio, hash_block);
+			return r;
+		}
+	}
 
 	aux = dm_bufio_get_aux_data(buf);
 
@@ -366,6 +382,7 @@ static int verity_verify_level(struct dm
 		}
 	}
 
+release_ok:
 	data += offset;
 	memcpy(want_digest, data, v->digest_size);
 	r = 0;
@@ -1761,7 +1778,7 @@ static struct target_type verity_target
 	.name		= "verity",
 /* Note: the LSMs depend on the singleton and immutable features */
 	.features	= DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
-	.version	= {1, 10, 0},
+	.version	= {1, 11, 0},
 	.module		= THIS_MODULE,
 	.ctr		= verity_ctr,
 	.dtr		= verity_dtr,

Re: [PATCH v2] dm-verity: do forward error correction on metadata I/O errors

[Sami Tolvanen]

On Mon, Feb 17, 2025 at 10:36:02PM +0100, Mikulas Patocka wrote:
> dm-verity: do forward error correction on metadata I/O errors
> 
> Do forward error correction if metadata I/O fails.
> 
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> 
> ---
>  drivers/md/dm-verity-target.c |   25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> Index: linux-2.6/drivers/md/dm-verity-target.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/dm-verity-target.c	2025-02-10 16:24:56.000000000 +0100
> +++ linux-2.6/drivers/md/dm-verity-target.c	2025-02-17 16:47:37.000000000 +0100
> @@ -311,7 +311,7 @@ static int verity_verify_level(struct dm
>  
>  	if (static_branch_unlikely(&use_bh_wq_enabled) && io->in_bh) {
>  		data = dm_bufio_get(v->bufio, hash_block, &buf);
> -		if (data == NULL) {
> +		if (IS_ERR_OR_NULL(data)) {

Thanks for adding the check, makes this easier to follow.

>  			/*
>  			 * In tasklet and the hash was not in the bufio cache.
>  			 * Return early and resume execution from a work-queue
> @@ -324,8 +324,24 @@ static int verity_verify_level(struct dm
>  						&buf, bio->bi_ioprio);
>  	}
>  
> -	if (IS_ERR(data))
> -		return PTR_ERR(data);
> +	if (IS_ERR(data)) {
> +		if (skip_unverified)
> +			return 1;
> +		r = PTR_ERR(data);
> +		data = dm_bufio_new(v->bufio, hash_block, &buf);
> +		if (IS_ERR(data))
> +			return r;
> +		if (verity_fec_decode(v, io, DM_VERITY_BLOCK_TYPE_METADATA,
> +				      hash_block, data) == 0) {
> +			aux = dm_bufio_get_aux_data(buf);
> +			aux->hash_verified = 1;
> +			goto release_ok;
> +		} else {
> +			dm_bufio_release(buf);
> +			dm_bufio_forget(v->bufio, hash_block);
> +			return r;
> +		}
> +	}
>  
>  	aux = dm_bufio_get_aux_data(buf);
>  
> @@ -366,6 +382,7 @@ static int verity_verify_level(struct dm
>  		}
>  	}
>  
> +release_ok:
>  	data += offset;
>  	memcpy(want_digest, data, v->digest_size);
>  	r = 0;
> @@ -1761,7 +1778,7 @@ static struct target_type verity_target
>  	.name		= "verity",
>  /* Note: the LSMs depend on the singleton and immutable features */
>  	.features	= DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
> -	.version	= {1, 10, 0},
> +	.version	= {1, 11, 0},
>  	.module		= THIS_MODULE,
>  	.ctr		= verity_ctr,
>  	.dtr		= verity_dtr,

Reviewed-by: Sami Tolvanen <samitolvanen@google.com>

Sami