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xdp: check prog type before updating BPF link 

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: 026a4c28e1 ("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>
This commit is contained in:
Toke Høiland-Jørgensen 2022-01-07 23:11:13 +01:00 committed by Greg Kroah-Hartman
parent b46b0ef69d
commit b87b59633e
1 changed files with 6 additions and 0 deletions
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6
net/core/dev.c
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@ -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);