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 C3DB2FA373D for ; Thu, 27 Oct 2022 22:55:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235176AbiJ0Wzl (ORCPT ); Thu, 27 Oct 2022 18:55:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233884AbiJ0Wzl (ORCPT ); Thu, 27 Oct 2022 18:55:41 -0400 Received: from mail-pg1-x549.google.com (mail-pg1-x549.google.com [IPv6:2607:f8b0:4864:20::549]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 09F18792DB for ; Thu, 27 Oct 2022 15:55:40 -0700 (PDT) Received: by mail-pg1-x549.google.com with SMTP id f186-20020a636ac3000000b0044adaa7d347so1492515pgc.14 for ; Thu, 27 Oct 2022 15:55:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=UyHHKto1OD9zfhqI+IeRFxKyzOJ9hzJRkZE5cd1gUiY=; b=IdlGsYzA7suWb1V+cdR6rTS/O6ecsngCSXAmC8Ce0keNTGEDB3UKyuSuJvDaSFFGKt fB/apJOgpPo73MwU430+vb71nEejIpR3kbzEmbRWnP3qXcVAitEv3rBgLg7kghCHeMFQ 7xmT4wQVF8oPY0PbAKs+PtVbKk98jqlRZy9NDS9AnmG8Jj9gWSlaoOD3+Ucdxx3cpYdq j04vy+y5kAcYEEhXnrOZWRMH6aKVQNdpAwMQfqXUMfkjHgJM8aU+jgxvHpywxz3ywKb9 9U1+Ac1fMt/GCkF6GD987yCmUyBXZOOPZg/jxY0p/Aqlza50uAa2D46kb1MtrjA/RbhO DiKA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=UyHHKto1OD9zfhqI+IeRFxKyzOJ9hzJRkZE5cd1gUiY=; b=8Qm9z1CljFtXnvwrsw6eJ8KIH0rouKVPG+VzbjrXeOVxJ7AGTZfsSlXAFE26W0QnV+ aTg9LdYQQLnKGj55FMWwT20L7FRAC1t9A8TM7jZNaVKpbDze5V/xZnmntnWMFnsG2ilU tjwdevGEKxj6bxHrERJwlBZ9JySk1/gOQtF5X7AYRrL411bDOmmyybU/Vsa4H9mMvXq9 O589aIxPSTxoKCeO7EPEikBrdvJh/JPldTm+5Ntncf/S6n/hf4LfRx/CMC+e3MEil6H1 BFUS9b39cJjO4ThM/QVO8XyB7oTEo3ib+gF2kbtOPoKtbIz/q8kAbfNGbx5L3X7alsUA 4o5g== X-Gm-Message-State: ACrzQf30dYQbbeTSL/n+DFiHD2nvpByhSinb5t3JfvS9aPtPh91uoh7K 744rSXy+VyyIiXFg60S9vkI4Fw5Fqky/bQlC3ANF/EG6KDr9KARS8pvOR58+HrdubxJ/ir01PJd y1GVY6ztzDnkEA/ZShsVjPOUCJQ0p1rVQZk5agLvpaQIHE5txgQ== X-Google-Smtp-Source: AMsMyM68N1r54qPC+XY+Wz1JHDtY5xjkqeJrcoqvW6kq7l8qC87XfHcXB8IZcoE+qHlV/5DIVULWSKw= X-Received: from sdf.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5935]) (user=sdf job=sendgmr) by 2002:a63:8341:0:b0:46f:d9e:b13f with SMTP id h62-20020a638341000000b0046f0d9eb13fmr19295422pge.389.1666911339422; Thu, 27 Oct 2022 15:55:39 -0700 (PDT) Date: Thu, 27 Oct 2022 15:55:37 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.38.1.273.g43a17bfeac-goog Message-ID: <20221027225537.353077-1-sdf@google.com> Subject: [PATCH bpf-next] bpf: make sure skb->len != 0 when redirecting to a tunneling device From: Stanislav Fomichev To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, Eric Dumazet , syzbot+f635e86ec3fa0a37e019@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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? 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 -- 2.38.1.273.g43a17bfeac-goog