From b87b59633e358f15e782df96f41733b228c06023 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= Date: Fri, 7 Jan 2022 23:11:13 +0100 Subject: [PATCH] xdp: check prog type before updating BPF link MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 382778edc8262b7535f00523e9eb22edba1b9816 upstream. The bpf_xdp_link_update() function didn't check the program type before updating the program, which made it possible to install any program type as an XDP program, which is obviously not good. Syzbot managed to trigger this by swapping in an LWT program on the XDP hook which would crash in a helper call. Fix this by adding a check and bailing out if the types don't match. Fixes: 026a4c28e1db ("bpf, xdp: Implement LINK_UPDATE for BPF XDP link") Reported-by: syzbot+983941aa85af6ded1fd9@syzkaller.appspotmail.com Acked-by: Andrii Nakryiko Signed-off-by: Toke Høiland-Jørgensen Link: https://lore.kernel.org/r/20220107221115.326171-1-toke@redhat.com Signed-off-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman --- net/core/dev.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/core/dev.c b/net/core/dev.c index e0878a500aa92..33dc2a3ff7d78 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -9636,6 +9636,12 @@ static int bpf_xdp_link_update(struct bpf_link *link, struct bpf_prog *new_prog, goto out_unlock; } old_prog = link->prog; + if (old_prog->type != new_prog->type || + old_prog->expected_attach_type != new_prog->expected_attach_type) { + err = -EINVAL; + goto out_unlock; + } + if (old_prog == new_prog) { /* no-op, don't disturb drivers */ bpf_prog_put(new_prog); -- 2.30.2