The unix_gid netlink upcall protocol has an explicit SUNRPC_A_UNIX_GID_NEGATIVE attribute for failed group lookups, and mountd sends it, but sunrpc_nl_parse_one_unix_gid() only allocates an empty group list for a flagged reply without propagating the flag into the entry, so it installs a valid positive entry with zero groups. Such an entry strips the uid of all supplementary groups until it is refreshed or expires: the same defect the previous patch fixes on the classic channel, on a transport that can say "lookup failed" explicitly. Set CACHE_NEGATIVE for flagged replies, as the netlink ip_map path already does for its negative flag. An empty GIDS list without the flag remains a positive entry. Fixes: 0850e8603cd7 ("sunrpc: add netlink upcall for the auth.unix.gid cache") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-fable-5 Signed-off-by: Ameer Hamza <ameer.hamza@truenas.com> Link: https://patch.msgid.link/20260814221953.108837-3-ameer.hamza@truenas.com Signed-off-by: Chuck Lever <cel@kernel.org>