Re: net: parsing IFLA_INET_CONF broken since 7.1 if NLA_F_NESTED not set

On Mon, 14 Sep 2026 15:21:59 +0100 Quentin Armitage wrote:

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_nested_deprecated() should be called, as it is
earlier in the function.

Please explain how you discovered the problem.
Is there some open source or closed source SW you're aware of which
breaks?