net/tcp: fix TCP-AO key deletion in VRFs

commit 94ad9e1 upstream.

TCP-AO keys with TCP_AO_KEYF_IFINDEX store the VRF L3 interface index in
l3index. tcp_ao_del_cmd() validates the supplied ifindex, but does not
assign it to its local l3index before matching keys.

As a result, deleting a key scoped to a non-default VRF always fails with
ENOENT because it is matched against l3index 0.

Fixes: 248411b ("net/tcp: Wire up l3index to TCP-AO")
Cc: stable@vger.kernel.org
Signed-off-by: Rastislav Szabo <rastislav.szabo@isovalent.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Acked-by: Dmitry Safonov <0x7f454c46@gmail.com>
Link: https://patch.msgid.link/20260822201119.272269-1-rastislav.szabo@isovalent.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: rastislavs

net/ipv4/tcp_ao.c

@@ -1854,6 +1854,9 @@ static int tcp_ao_del_cmd(struct sock *sk, unsigned short int family,
 	if (cmd.ifindex && !(cmd.keyflags & TCP_AO_KEYF_IFINDEX))
 		return -EINVAL;
 
+	if (cmd.keyflags & TCP_AO_KEYF_IFINDEX)
+		l3index = cmd.ifindex;
+
 	ao_info = setsockopt_ao_info(sk);
 	if (IS_ERR(ao_info))
 		return PTR_ERR(ao_info);