[PATCH 2/2] erofs-utils: lib: oci: restrict `ocierofs_io_open()` to single-layer images

[zhaoyifan (H)]

Hi Xiang,

Could you consider apply this patch first? As we disscussed before it 
prevents subprocess

from segfault while oci.layer or oci.blob is not specified in mount.erofs.


We would better not add an error print for now until we refactor the 
current codebase and

fork one child process for both netlink and ioctl, otherwise double 
error messages are shown.


Thanks,

Yifan Zhao


On 2025/12/16 15:05, Yifan Zhao wrote:
> When mounting an OCI image with `mount.erofs -t erofs.nbd` without
> specifying either `oci.layer=` or `oci.blob=`, a segfault occurs in the
> `ocierofs_download_blob_range() → ocierofs_find_layer_by_digest()` call
> path due to an empty `ctx->blob_digest`.
>
> As mounting multi-layer OCI images is not yet supported, let's exit
> early in `ocierofs_io_open()` with an error in this case.
>
> Signed-off-by: Yifan Zhao <zhaoyifan28 at huawei.com>
> ---
>   lib/remotes/oci.c | 19 +++++++++++++------
>   1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/lib/remotes/oci.c b/lib/remotes/oci.c
> index d5afd6a..ce7a1a5 100644
> --- a/lib/remotes/oci.c
> +++ b/lib/remotes/oci.c
> @@ -1479,16 +1479,18 @@ int ocierofs_io_open(struct erofs_vfile *vfile, const struct ocierofs_config *cf
>   		return -ENOMEM;
>   
>   	err = ocierofs_init(ctx, cfg);
> -	if (err) {
> -		free(ctx);
> -		return err;
> +	if (err)
> +		goto out;
> +
> +	if (!ctx->blob_digest) {
> +		err = -EINVAL;
> +		goto out;
>   	}
>   
>   	oci_iostream = calloc(1, sizeof(*oci_iostream));
>   	if (!oci_iostream) {
> -		ocierofs_ctx_cleanup(ctx);
> -		free(ctx);
> -		return -ENOMEM;
> +		err = -ENOMEM;
> +		goto out;
>   	}
>   
>   	oci_iostream->ctx = ctx;
> @@ -1496,6 +1498,11 @@ int ocierofs_io_open(struct erofs_vfile *vfile, const struct ocierofs_config *cf
>   	*vfile = (struct erofs_vfile){.ops = &ocierofs_io_vfops};
>   	*(struct ocierofs_iostream **)vfile->payload = oci_iostream;
>   	return 0;
> +
> +out:
> +	ocierofs_ctx_cleanup(ctx);
> +	free(ctx);
> +	return err;
>   }
>   
>   char *ocierofs_encode_userpass(const char *username, const char *password)