File _service:obs_scm:backport-accept-NULL-argument-... of Package libnl3

File _service:obs_scm:backport-accept-NULL-argument-in-nla_nest_cancel-for-robustness.patch of Package libnl3

From 6af26981e727149e2e3fdfac85e2ef86b3828b11 Mon Sep 17 00:00:00 2001
From: Thomas Haller <thaller@redhat.com>
Date: Wed, 26 Jul 2023 16:17:18 +0200
Subject: [PATCH] lib: accept NULL argument in nla_nest_cancel() for robustness
 
Previously, a NULL argument would most likely also do thing, but it also
hits undefined behavior.
 
Conflict:NA
Reference:https://github.com/thom311/libnl/commit/6af26981e727149e2e3fdfac85e2ef86b3828b11

---
 lib/attr.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/lib/attr.c b/lib/attr.c
index a4f5852..2b2d538 100644
--- a/lib/attr.c
+++ b/lib/attr.c
@@ -996,6 +996,15 @@ void nla_nest_cancel(struct nl_msg *msg, const struct nlattr *attr)
 {
 	ssize_t len;
 
+	if (!attr) {
+		/* For robustness, allow a NULL attr to do nothing. NULL is also
+		 * what nla_nest_start() when out of buffer space.
+		 *
+		 * Warning, before libnl-3.8, the function did not accept NULL!
+		 * If you care, catch NULL yourself. */
+		return;
+	}
+
 	len = (char *) nlmsg_tail(msg->nm_nlh) - (char *) attr;
 	if (len < 0)
 		BUG();
-- 
2.33.0