[PATCH v3 05/14] NFSD: report listener creation failures through extack

[Jeff Layton <jlayton@kernel.org>]

nfsd_nl_listener_set_doit() returns the raw errno from
svc_xprt_create_from_sa() and sets no extack. A failed LISTENER_SET
therefore tells userland only "Address already in use", or whatever else
the transport returned. It never tells userland which entry failed.

Record the attribute and the transport name of the entry whose errno the
call returns, and report both after the loop. NL_SET_BAD_ATTR() names the
entry, which the message alone cannot do: a request can carry several
entries with the same transport name.

The rejections in nfsd_nl_validate_listeners() other than -E2BIG and the
unsupported transport name still carry no extack. This patch does not
change them.

Assisted-by: LLM
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/nfsctl.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index d8135f38e69f..6cbdcee4b733 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -2089,7 +2089,9 @@ static int nfsd_nl_validate_listeners(struct genl_info *info)
 int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
 {
 	struct net *net = genl_info_net(info);
+	const struct nlattr *bad_attr = NULL;
 	struct svc_xprt *xprt, *tmp;
+	const char *bad_xprt = NULL;
 	const struct nlattr *attr;
 	struct svc_serv *serv;
 	LIST_HEAD(permsocks);
@@ -2208,8 +2210,22 @@ int nfsd_nl_listener_set_doit(struct sk_buff *skb, struct genl_info *info)
 		ret = svc_xprt_create_from_sa(serv, xcl_name, net, sa, 0,
 					      current_cred());
 		/* always save the latest error */
-		if (ret < 0)
+		if (ret < 0) {
+			bad_attr = attr;
+			bad_xprt = xcl_name;
 			err = ret;
+		}
+	}
+
+	/*
+	 * The ack carries the errno of the last entry that failed. Point at
+	 * that entry as well, since several entries can share a transport
+	 * name and the errno alone cannot tell them apart.
+	 */
+	if (err) {
+		NL_SET_BAD_ATTR(info->extack, bad_attr);
+		NL_SET_ERR_MSG_FMT(info->extack, "cannot create %s listener",
+				   bad_xprt);
 	}
 
 	if (!serv->sv_nrthreads && list_empty(&nn->nfsd_serv->sv_permsocks))

-- 
2.55.0