From e58483c4fb697652a8e19c6cdc55a06d3af7e5d8 Mon Sep 17 00:00:00 2001
From: Ryan Moeller <freqlabs@FreeBSD.org>
Date: Sat, 24 Oct 2020 16:17:07 +0000
Subject: [PATCH] sysctl+kern_sysctl: Honor SKIP for descendant nodes

Ensure we also skip descendants of SKIP nodes when iterating through children
of an explicitly specified node.

Reported by:	np
Reviewed by:	np
MFC after:	1 week
Sponsored by:	iXsystems, Inc.
Differential Revision:	https://reviews.freebsd.org/D26833
---
 sbin/sysctl/sysctl.c   | 17 +++++++++++++++--
 sys/kern/kern_sysctl.c |  8 ++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/sbin/sysctl/sysctl.c b/sbin/sysctl/sysctl.c
index 2f4a61220714..545030b2f105 100644
--- a/sbin/sysctl/sysctl.c
+++ b/sbin/sysctl/sysctl.c
@@ -952,6 +952,7 @@ oidfmt(int *oid, int len, char *fmt, u_int *kind)
 static int
 show_var(int *oid, int nlen, bool honor_skip)
 {
+	static int skip_len = 0, skip_oid[CTL_MAXNAME];
 	u_char buf[BUFSIZ], *val, *oval, *p;
 	char name[BUFSIZ], fmt[BUFSIZ];
 	const char *sep, *sep1, *prntype;
@@ -1021,9 +1022,21 @@ show_var(int *oid, int nlen, bool honor_skip)
 		return (0);
 	}
 
+	/* keep track of encountered skip nodes, ignoring descendants */
+	if (skip_len == 0 && (kind & CTLFLAG_SKIP) != 0) {
+		/* Save this oid so we can skip descendants. */
+		skip_len = nlen * sizeof(int);
+		memcpy(skip_oid, oid, skip_len);
+	}
+
 	/* bail before fetching the value if we're honoring skip */
-	if (honor_skip && (kind & CTLFLAG_SKIP) != 0)
-		return (1);
+	if (honor_skip) {
+		if (0 < skip_len && skip_len <= nlen * (int)sizeof(int) &&
+		    memcmp(skip_oid, oid, skip_len) == 0)
+			return (1);
+		/* Not a skip node or descendant of a skip node. */
+		skip_len = 0;
+	}
 
 	/* don't fetch opaques that we don't know how to print */
 	if (ctltype == CTLTYPE_OPAQUE) {
diff --git a/sys/kern/kern_sysctl.c b/sys/kern/kern_sysctl.c
index aec19024bdcf..2b8a212e59d2 100644
--- a/sys/kern/kern_sysctl.c
+++ b/sys/kern/kern_sysctl.c
@@ -1126,9 +1126,13 @@ sysctl_sysctl_next_ls(struct sysctl_oid_list *lsp, int *name, u_int namelen,
 			 * We have reached a node with a full name match and are
 			 * looking for the next oid in its children.
 			 *
+			 * For CTL_SYSCTL_NEXTNOSKIP we are done.
+			 *
 			 * For CTL_SYSCTL_NEXT we skip CTLTYPE_NODE (unless it
 			 * has a handler) and move on to the children.
 			 */
+			if (!honor_skip)
+				return (0);
 			if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE) 
 				return (0);
 			if (oidp->oid_handler) 
@@ -1163,9 +1167,13 @@ sysctl_sysctl_next_ls(struct sysctl_oid_list *lsp, int *name, u_int namelen,
 			/*
 			 * We have reached the next oid.
 			 *
+			 * For CTL_SYSCTL_NEXTNOSKIP we are done.
+			 *
 			 * For CTL_SYSCTL_NEXT we skip CTLTYPE_NODE (unless it
 			 * has a handler) and move on to the children.
 			 */
+			if (!honor_skip)
+				return (0);
 			if ((oidp->oid_kind & CTLTYPE) != CTLTYPE_NODE)
 				return (0);
 			if (oidp->oid_handler)
-- 
2.41.0