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

[Richard Cheng <icheng@nvidia.com>]

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].

[1]: https://lore.kernel.org/all/20260624134737.49166-1-icheng@nvidia.com/
Signed-off-by: Richard Cheng <icheng@nvidia.com>
---
 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