[PATCH nfs-utils] nfsdctl: inspect only the command request policy

[Giuseppe Piscitelli <ooonea@gmail.com>]

CTRL_CMD_GETPOLICY also describes nested attribute policies. Counting
those attributes as command capabilities can enable unsupported flags.
Select the do-operation policy index before computing its maximum, and
keep that index across dump messages.

Signed-off-by: Giuseppe Piscitelli <ooonea@gmail.com>
Assisted-by: OpenAI Codex
---
A four-case callback harness passed with this change (one case passed
before). An isolated Linux 7.3 VM passed nfsdctl threads 0/autostart and
NFSv3/v4.2 write/read, sync and root-squash checks with nfs-utils 3.1.1.
These results are from October 23; no new build or runtime test was run.

 utils/nfsdctl/nfsdctl.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/utils/nfsdctl/nfsdctl.c b/utils/nfsdctl/nfsdctl.c
index 505b38d..67e2a0b 100644
--- a/utils/nfsdctl/nfsdctl.c
+++ b/utils/nfsdctl/nfsdctl.c
@@ -561,10 +561,15 @@ static int nfsd_nl_family_setup(struct nl_sock *sock)
 	return nfsd_nl_family;
 }
 
+struct nfsd_cmd_policy {
+	int *max_nlattr;
+	int policy_index;
+};
+
 static int getpolicy_handler(struct nl_msg *msg, void *arg)
 {
 	struct genlmsghdr *gnlh = nlmsg_data(nlmsg_hdr(msg));
-	int *max_nlattr = arg;
+	struct nfsd_cmd_policy *policy = arg;
 	struct nlattr *attr;
 	int rem;
 
@@ -572,13 +577,23 @@ static int getpolicy_handler(struct nl_msg *msg, void *arg)
 		struct nlattr *a, *b;
 		int i, j;
 
+		if (nla_type(attr) == CTRL_ATTR_OP_POLICY) {
+			nla_for_each_nested(a, attr, i) {
+				b = nla_find(nla_data(a), nla_len(a),
+					     CTRL_ATTR_POLICY_DO);
+				if (b)
+					policy->policy_index = nla_get_u32(b);
+			}
+		}
 		if (nla_type(attr) == CTRL_ATTR_POLICY) {
 			nla_for_each_nested(a, attr, i) {
+				if (nla_type(a) != policy->policy_index)
+					continue;
 				nla_for_each_nested(b, a, j) {
 					int idx = nla_type(b);
 
-					if (*max_nlattr < idx)
-						*max_nlattr = idx;
+					if (*policy->max_nlattr < idx)
+						*policy->max_nlattr = idx;
 				}
 			}
 		}
@@ -589,6 +604,7 @@ static int getpolicy_handler(struct nl_msg *msg, void *arg)
 static int query_nfsd_nl_cmd_policy(struct nl_sock *sock, int cmd,
 				    int *max_nlattr)
 {
+	struct nfsd_cmd_policy policy = { max_nlattr, -1 };
 	struct genlmsghdr *ghdr;
 	struct nlmsghdr *nlh;
 	struct nl_msg *msg;
@@ -625,7 +641,7 @@ static int query_nfsd_nl_cmd_policy(struct nl_sock *sock, int cmd,
 	nl_cb_err(cb, NL_CB_CUSTOM, error_handler, &ret);
 	nl_cb_set(cb, NL_CB_FINISH, NL_CB_CUSTOM, finish_handler, &ret);
 	nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_handler, &ret);
-	nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, getpolicy_handler, max_nlattr);
+	nl_cb_set(cb, NL_CB_VALID, NL_CB_CUSTOM, getpolicy_handler, &policy);
 
 	while (ret > 0)
 		nl_recvmsgs(sock, cb);
-- 
2.54.0