[PATCH 0/2] dm era: fix metadata_open NULL deref and error propagation

[PATCH 0/2] dm era: fix metadata_open NULL deref and error propagation

[ghuicao]

From: Cao Guanghui <caoguanghui@kylinos.cn>

This series fixes two issues in dm-era:

1. metadata_open() returns NULL on kzalloc failure, but era_ctr() only
   checks IS_ERR(), causing a NULL pointer dereference.

2. era_ctr() replaces actual error codes from dm_get_device() and
   dm_set_target_max_io_len() with hardcoded -EINVAL, making diagnosis
   harder for users.

Both are straightforward fixes with no functional change for the
success path.

Cao Guanghui (2):
  dm era: fix NULL pointer dereference in metadata_open()
  dm era: fix error code propagation in era_ctr()

 drivers/md/dm-era-target.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

-- 
2.25.1

[PATCH 1/2] dm era: fix NULL pointer dereference in metadata_open()

[ghuicao]

From: Cao Guanghui <caoguanghui@kylinos.cn>

metadata_open() returns NULL when kzalloc_obj() fails, but the
caller era_ctr() only checks IS_ERR(md).  Since IS_ERR(NULL)
returns false, the NULL pointer is treated as a valid result
and later assigned to era->md, leading to a NULL pointer
dereference when the metadata is accessed.

Fix this by returning ERR_PTR(-ENOMEM) on allocation failure,
consistent with dm-cache-metadata.c, dm-thin-metadata.c, and
dm-clone-metadata.c which all use ERR_PTR(-ENOMEM) for the
same pattern.

Fixes: eec40579d848 ("dm: add era target")
Signed-off-by: Cao Guanghui <caoguanghui@kylinos.cn>
---
 drivers/md/dm-era-target.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-era-target.c b/drivers/md/dm-era-target.c
index 05285c04ff2c..08ce96e8cf4f 100644
--- a/drivers/md/dm-era-target.c
+++ b/drivers/md/dm-era-target.c
@@ -810,8 +810,10 @@ static struct era_metadata *metadata_open(struct block_device *bdev,
 	int r;
 	struct era_metadata *md = kzalloc_obj(*md);
 
-	if (!md)
-		return NULL;
+	if (!md) {
+		DMERR("could not allocate metadata struct");
+		return ERR_PTR(-ENOMEM);
+	}
 
 	md->bdev = bdev;
 	md->block_size = block_size;
-- 
2.25.1

Re: [PATCH 1/2] dm era: fix NULL pointer dereference in metadata_open()

[Su Yue]

On Wed 17 Jun 2026 at 14:00, ghuicao@163.com wrote:

> From: Cao Guanghui <caoguanghui@kylinos.cn>
>
> metadata_open() returns NULL when kzalloc_obj() fails, but the
> caller era_ctr() only checks IS_ERR(md).  Since IS_ERR(NULL)
> returns false, the NULL pointer is treated as a valid result
> and later assigned to era->md, leading to a NULL pointer
> dereference when the metadata is accessed.
>
> Fix this by returning ERR_PTR(-ENOMEM) on allocation failure,
> consistent with dm-cache-metadata.c, dm-thin-metadata.c, and
> dm-clone-metadata.c which all use ERR_PTR(-ENOMEM) for the
> same pattern.
>
> Fixes: eec40579d848 ("dm: add era target")
> Signed-off-by: Cao Guanghui <caoguanghui@kylinos.cn>
>
Reviewed-by: Su Yue <glass.su@suse.com>

> ---
>  drivers/md/dm-era-target.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/dm-era-target.c 
> b/drivers/md/dm-era-target.c
> index 05285c04ff2c..08ce96e8cf4f 100644
> --- a/drivers/md/dm-era-target.c
> +++ b/drivers/md/dm-era-target.c
> @@ -810,8 +810,10 @@ static struct era_metadata 
> *metadata_open(struct block_device *bdev,
>  	int r;
>  	struct era_metadata *md = kzalloc_obj(*md);
>
> -	if (!md)
> -		return NULL;
> +	if (!md) {
> +		DMERR("could not allocate metadata struct");
> +		return ERR_PTR(-ENOMEM);
> +	}
>
>  	md->bdev = bdev;
>  	md->block_size = block_size;

[PATCH 2/2] dm era: fix error code propagation in era_ctr()

[ghuicao]

From: Cao Guanghui <caoguanghui@kylinos.cn>

era_ctr() replaces the actual error codes returned by dm_get_device()
and dm_set_target_max_io_len() with hardcoded -EINVAL, discarding
the real reason for the failure (e.g. -ENODEV, -ENOMEM).  This makes
it harder for users to diagnose problems and is inconsistent with
other dm targets (dm-thin, dm-verity, dm-flakey, dm-ebs) which
propagate the original error.

Fix all three sites to return 'r' instead of -EINVAL.

Signed-off-by: Cao Guanghui <caoguanghui@kylinos.cn>
---
 drivers/md/dm-era-target.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-era-target.c b/drivers/md/dm-era-target.c
index 08ce96e8cf4f..4eb1c4f90e1b 100644
--- a/drivers/md/dm-era-target.c
+++ b/drivers/md/dm-era-target.c
@@ -1488,7 +1488,7 @@ static int era_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	if (r) {
 		ti->error = "Error opening metadata device";
 		era_destroy(era);
-		return -EINVAL;
+		return r;
 	}
 
 	r = dm_get_device(ti, argv[1], BLK_OPEN_READ | BLK_OPEN_WRITE,
@@ -1496,7 +1496,7 @@ static int era_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	if (r) {
 		ti->error = "Error opening data device";
 		era_destroy(era);
-		return -EINVAL;
+		return r;
 	}
 
 	r = sscanf(argv[2], "%u%c", &era->sectors_per_block, &dummy);
@@ -1510,7 +1510,7 @@ static int era_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	if (r) {
 		ti->error = "could not set max io len";
 		era_destroy(era);
-		return -EINVAL;
+		return r;
 	}
 
 	if (!valid_block_size(era->sectors_per_block)) {
-- 
2.25.1

Re: [PATCH 2/2] dm era: fix error code propagation in era_ctr()

[Su Yue]

On Wed 17 Jun 2026 at 14:00, ghuicao@163.com wrote:

> From: Cao Guanghui <caoguanghui@kylinos.cn>
>
> era_ctr() replaces the actual error codes returned by 
> dm_get_device()
> and dm_set_target_max_io_len() with hardcoded -EINVAL, 
> discarding
> the real reason for the failure (e.g. -ENODEV, -ENOMEM).  This 
> makes
> it harder for users to diagnose problems and is inconsistent 
> with
> other dm targets (dm-thin, dm-verity, dm-flakey, dm-ebs) which
> propagate the original error.
>
> Fix all three sites to return 'r' instead of -EINVAL.
>
> Signed-off-by: Cao Guanghui <caoguanghui@kylinos.cn>
>
Reviewed-by: Su Yue <glass.su@suse.com>

> ---
>  drivers/md/dm-era-target.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/dm-era-target.c 
> b/drivers/md/dm-era-target.c
> index 08ce96e8cf4f..4eb1c4f90e1b 100644
> --- a/drivers/md/dm-era-target.c
> +++ b/drivers/md/dm-era-target.c
> @@ -1488,7 +1488,7 @@ static int era_ctr(struct dm_target *ti, 
> unsigned int argc, char **argv)
>  	if (r) {
>  		ti->error = "Error opening metadata device";
>  		era_destroy(era);
> -		return -EINVAL;
> +		return r;
>  	}
>
>  	r = dm_get_device(ti, argv[1], BLK_OPEN_READ | BLK_OPEN_WRITE,
> @@ -1496,7 +1496,7 @@ static int era_ctr(struct dm_target *ti, 
> unsigned int argc, char **argv)
>  	if (r) {
>  		ti->error = "Error opening data device";
>  		era_destroy(era);
> -		return -EINVAL;
> +		return r;
>  	}
>
>  	r = sscanf(argv[2], "%u%c", &era->sectors_per_block, &dummy);
> @@ -1510,7 +1510,7 @@ static int era_ctr(struct dm_target *ti, 
> unsigned int argc, char **argv)
>  	if (r) {
>  		ti->error = "could not set max io len";
>  		era_destroy(era);
> -		return -EINVAL;
> +		return r;
>  	}
>
>  	if (!valid_block_size(era->sectors_per_block)) {