Syzbot found an issue [1]: fq_codel_drop() try to drop a flow whitout any skbs, that is, the flow->head is null. The root cause, as the [2] says, is because that bpf_prog_test_run_skb() run a bpf prog which redirects empty skbs. So we should determine whether the length of the packet modified by bpf prog is valid before forwarding it directly. LINK: [1] https://syzkaller.appspot.com/bug?id=0b84da80c2917757915afa89f7738a9d16ec96c5 LINK: [2] https://www.spinics.net/lists/netdev/msg777503.html Reported-by: syzbot+7a12909485b94426aceb@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Zhengchao Shao <shaozhengchao@xxxxxxxxxx> --- v1: should not check len in fast path net/bpf/test_run.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 2ca96acbc50a..750d7d173a20 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -1152,6 +1152,12 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr, ret = convert___skb_to_skb(skb, ctx); if (ret) goto out; + + if (skb->len == 0) { + ret = -EINVAL; + goto out; + } + ret = bpf_test_run(prog, skb, repeat, &retval, &duration, false); if (ret) goto out; -- 2.17.1
