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

[Su Yue <l@damenly.org>]

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;