Re: [ndctl PATCH] test/fwctl: Add Get Feature OOB rejection regression test

[Alison Schofield]

On Wed, Jun 24, 2026 at 10:00:06PM +0800, Richard Cheng wrote:
> Add a negative case to the CXL fwctl test that issues a Get Feature
> FWCTL_RPC with out_len == offset(struct fwctl_rpc_cxl_out, payload) and
> a non-zero count. The kernel must reject this with -EINVAL instead of
> writing the feature payload past the rpc_out buffer.
> 
> This is the userspace regression test for corresponding kernel fix [1].

Hi Richard,

I just finished reviewing the now 3 piece series[2], that [1] is now
a piece of.

One suggestion on top of the kver gating suggested in prior response
is to add a companion negative case for the Set Feature bounds fix
in the same series. Same shape as this one, ie build a normal Set
Feature RPC, set out_len to 0, expect -EINVAL. It's a stronger backstop
than the Get case, too because before the fix an out_len of 0 makes
kvzalloc() return ZERO_SIZE_PTR, which passes the !rpc_out check, and
the header write then oopses rather than just returning a wrong status.
Gate it on the same kver helper.

I'm stopping short of suggesting a test for the third patch (the Get
Feature per-iteration clamp). That one looks like it needs a
multi-transfer feature and a device that over returns on the last chunk,
neither possible without a cxl_test mock change.

-- Alison

> [1]: https://lore.kernel.org/all/20260624134737.49166-1-icheng@xxxxxxxxxx/
[2]: https://lore.kernel.org/linux-cxl/20260626104102.53892-1-icheng@xxxxxxxxxx/#r


> Signed-off-by: Richard Cheng <icheng@xxxxxxxxxx>
> ---
>  test/fwctl.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
> 
> diff --git a/test/fwctl.c b/test/fwctl.c
> index 979c1a6..69d0048 100644
> --- a/test/fwctl.c
> +++ b/test/fwctl.c
> @@ -5,6 +5,7 @@
>  #include <stdio.h>
>  #include <endian.h>
>  #include <stdint.h>
> +#include <stddef.h>
>  #include <stdlib.h>
>  #include <syslog.h>
>  #include <string.h>
> @@ -207,6 +208,45 @@ out:
>  	return rc;
>  }
>  
> +static int cxl_fwctl_rpc_get_feature_oob(int fd, struct test_feature *feat_ctx)
> +{
> +	struct cxl_mbox_get_feat_in *feat_in;
> +	struct fwctl_rpc_cxl_out *out;
> +	size_t out_size, in_size;
> +	struct fwctl_rpc_cxl *in;
> +	struct fwctl_rpc *rpc;
> +	int rc;
> +
> +	in_size = sizeof(*in) + sizeof(*feat_in);
> +	/* header only => zero payload room */
> +	out_size = offsetof(struct fwctl_rpc_cxl_out, payload);
> +
> +	rpc = get_prepped_command(in_size, out_size,
> +				  CXL_MBOX_OPCODE_GET_FEATURE);
> +	if (!rpc)
> +		return -ENXIO;
> +
> +	in = (struct fwctl_rpc_cxl *)rpc->in;
> +	out = (struct fwctl_rpc_cxl_out *)rpc->out;
> +
> +	feat_in = &in->get_feat_in;
> +	uuid_copy(feat_in->uuid, feat_ctx->uuid);
> +	/* non-zero count that exceeds the zero payload room */
> +	feat_in->count = feat_ctx->get_size;
> +
> +	rc = send_command(fd, rpc, out);
> +	free_rpc(rpc);
> +
> +	if (rc == -EINVAL)
> +		return 0;
> +	if (rc == 0) {
> +		fprintf(stderr, "Get Feature with undersized out_len was not rejected\n");
> +		return -ENXIO;
> +	}
> +	fprintf(stderr, "Get Feature OOB rejection test: unexpected rc %d\n", rc);
> +	return rc;
> +}
> +
>  static int cxl_fwctl_rpc_set_test_feature(int fd, struct test_feature *feat_ctx)
>  {
>  	struct cxl_mbox_set_feat_in *feat_in;
> @@ -393,6 +433,12 @@ static int test_fwctl_features(struct cxl_memdev *memdev)
>  		goto out;
>  	}
>  
> +	rc = cxl_fwctl_rpc_get_feature_oob(fd, &feat_ctx);
> +	if (rc) {
> +		fprintf(stderr, "Failed Get Feature OOB rejection test: %d\n", rc);
> +		goto out;
> +	}
> +
>  out:
>  	close(fd);
>  	return rc;
> 
> base-commit: 8ad90e54f0ff4f7291e7f21d44d769d10f24e2b6
> -- 
> 2.43.0
>