From: Toke Høiland-Jørgensen Date: Fri, 7 Jan 2022 22:11:13 +0000 (+0100) Subject: xdp: check prog type before updating BPF link X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=382778edc8262b7535f00523e9eb22edba1b9816;p=linux.git xdp: check prog type before updating BPF link 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 --- diff --git a/net/core/dev.c b/net/core/dev.c index 84a0d9542fe94..1baab07820f65 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -8981,6 +8981,12 @@ 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);