From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A28DC433FE for ; Tue, 1 Nov 2022 20:29:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229534AbiKAU3F (ORCPT ); Tue, 1 Nov 2022 16:29:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229741AbiKAU2p (ORCPT ); Tue, 1 Nov 2022 16:28:45 -0400 Received: from out0.migadu.com (out0.migadu.com [94.23.1.103]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9BA7C167F6 for ; Tue, 1 Nov 2022 13:28:44 -0700 (PDT) Message-ID: <2efac61c-a477-d3c1-4270-3c98998e6497@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1667334522; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+7VweGWTu3qLunb4EHktFAdB1jk/2Ru+GS1K3CsODsw=; b=LAtVugb2OBnZwcSD4TJRd8SEUyUNMCYlInr1Ai1Ulkx4O+n2hyysJMNgP5O6MJRMxQ94zi 1fWWiC6iIS/++JZzCqVqUjsvmaceZfCMxj9Mas4QhxaD+lftim/o0xY0DQXPGFq0fiknNP 6+HvYq1R2BKy4+puWJxt4fiVBmQNeaA= Date: Tue, 1 Nov 2022 13:28:38 -0700 MIME-Version: 1.0 Subject: Re: [PATCH bpf-next] bpf: make sure skb->len != 0 when redirecting to a tunneling device Content-Language: en-US To: Stanislav Fomichev Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, haoluo@google.com, jolsa@kernel.org, Eric Dumazet , syzbot+f635e86ec3fa0a37e019@syzkaller.appspotmail.com, bpf@vger.kernel.org References: <20221027225537.353077-1-sdf@google.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: <20221027225537.353077-1-sdf@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 10/27/22 3:55 PM, Stanislav Fomichev wrote: > syzkaller managed to trigger another case where skb->len == 0 > when we enter __dev_queue_xmit: > > WARNING: CPU: 0 PID: 2470 at include/linux/skbuff.h:2576 skb_assert_len include/linux/skbuff.h:2576 [inline] > WARNING: CPU: 0 PID: 2470 at include/linux/skbuff.h:2576 __dev_queue_xmit+0x2069/0x35e0 net/core/dev.c:4295 > > Call Trace: > dev_queue_xmit+0x17/0x20 net/core/dev.c:4406 > __bpf_tx_skb net/core/filter.c:2115 [inline] > __bpf_redirect_no_mac net/core/filter.c:2140 [inline] > __bpf_redirect+0x5fb/0xda0 net/core/filter.c:2163 > ____bpf_clone_redirect net/core/filter.c:2447 [inline] > bpf_clone_redirect+0x247/0x390 net/core/filter.c:2419 > bpf_prog_48159a89cb4a9a16+0x59/0x5e > bpf_dispatcher_nop_func include/linux/bpf.h:897 [inline] > __bpf_prog_run include/linux/filter.h:596 [inline] > bpf_prog_run include/linux/filter.h:603 [inline] > bpf_test_run+0x46c/0x890 net/bpf/test_run.c:402 > bpf_prog_test_run_skb+0xbdc/0x14c0 net/bpf/test_run.c:1170 > bpf_prog_test_run+0x345/0x3c0 kernel/bpf/syscall.c:3648 > __sys_bpf+0x43a/0x6c0 kernel/bpf/syscall.c:5005 > __do_sys_bpf kernel/bpf/syscall.c:5091 [inline] > __se_sys_bpf kernel/bpf/syscall.c:5089 [inline] > __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5089 > do_syscall_64+0x54/0x70 arch/x86/entry/common.c:48 > entry_SYSCALL_64_after_hwframe+0x61/0xc6 > > The reproducer doesn't really reproduce outside of syzkaller > environment, so I'm taking a guess here. It looks like we > do generate correct ETH_HLEN-sized packet, but we redirect > the packet to the tunneling device. Before we do so, we > __skb_pull l2 header and arrive again at skb->len == 0. > Doesn't seem like we can do anything better than having > an explicit check after __skb_pull? hmm... I recall there was similar report but I didn't follow those earlier fixes and discussion. Not sure if this has been considered: If this skb can only happen in the bpf_prog_test_run (?), how about ensure that the skb will at least have some header after l2 header in bpf_prog_test_run_skb(). Adding some headers/bytes if the data_size_in does not have it. This may break some external test cases that somehow has no l3/4? test_progs should be mostly fine considering they are using the pkt_v[46] in network_helpers.h. > > Cc: Eric Dumazet > Reported-by: syzbot+f635e86ec3fa0a37e019@syzkaller.appspotmail.com > Signed-off-by: Stanislav Fomichev > --- > net/core/filter.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/net/core/filter.c b/net/core/filter.c > index bb0136e7a8e4..cb3b635e35be 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -2126,6 +2126,10 @@ static int __bpf_redirect_no_mac(struct sk_buff *skb, struct net_device *dev, > > if (mlen) { > __skb_pull(skb, mlen); > + if (unlikely(!skb->len)) { > + kfree_skb(skb); > + return -ERANGE; > + } > > /* At ingress, the mac header has already been pulled once. > * At egress, skb_pospull_rcsum has to be done in case that