From: Toke Høiland-Jørgensen toke@redhat.com
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 andrii@kernel.org Signed-off-by: Toke Høiland-Jørgensen toke@redhat.com Link: https://lore.kernel.org/r/20220107221115.326171-1-toke@redhat.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/core/dev.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/net/core/dev.c +++ b/net/core/dev.c @@ -9339,6 +9339,12 @@ static int bpf_xdp_link_update(struct bp 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);