[PATCH v2] net: parsing IFLA_INET_CONF broken since 7.1 if NLA_F_NESTED not set

Commit fa8fca88714c ("ipv4: validate IPV4_DEVCONF attributes properly") changed
inet_validate_link_af() to call nla_parse_nested() rather than
nla_for_each_nested() for IFLA_INET_CONF. A side effect of this change is that
the code now checks that NLA_F_NESTED is set for IFLA_INET_CONF, and rejects the
message if it is not, whereas previously there was no check for NLA_F_NESTED
being set.

The consequence of this is that code which worked prior to Linux 7.1, albeit
erroneously not setting NLA_F_NESTED now fails.

In order to maintain backward compatibility, rather than calling
nla_parse_nested(), nla_parse() is called.

From 498a8cffcdbbc3265d2a4747ba5ded6f562af3a7 Mon Sep 17 00:00:00 2001
From: Quentin Armitage <redacted>
Date: Mon, 14 Sep 2026 18:19:53 +0100
Subject: [PATCH v2] net: allow IFLA_INET_CONF messages when NLA_F_NESTED unset

Commit fa8fca88714c ("ipv4: validate IPV4_DEVCONF attributes properly")
added validation of IFLA_INET_CONF attributes, and in the process
changed the call of nla_for_each_nested() to nla_parse_nested(). A
side effect of this change is that the IFLA_INET_CONF option is now
tested for NLA_F_NESTED being set, and fails if it is not. Prior to the
commit there was no check of NLA_F_NESTED.

Change nla_parse_nested() to nla_parse(). This restores the previous
functionality of not checking NLA_F_NESTED, thereby allowing code that
(incorrectly) doesn't set NLA_F_NESTED to continue to work.

Signed-off-by: Quentin Armitage <redacted>
---
 net/ipv4/devinet.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index a90be57c63be..5b6b11c943e4 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c

@@ -2117,9 +2117,10 @@ static int inet_validate_link_af(const struct net_device

*dev,
 		return err;
 
 	if (tb[IFLA_INET_CONF]) {
-		err = nla_parse_nested(nested_tb, IPV4_DEVCONF_MAX,
-				       tb[IFLA_INET_CONF], inet_devconf_policy,
-				       extack);
+		err = nla_parse(nested_tb, IPV4_DEVCONF_MAX,
+				nla_data(tb[IFLA_INET_CONF]),
+				nla_len(tb[IFLA_INET_CONF]),
+				inet_devconf_policy, extack);
 
 		if (err < 0)
 			return err;
-- 
2.55.0