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 ADD6AEB64D8 for ; Wed, 21 Jun 2023 10:21:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230511AbjFUKVC (ORCPT ); Wed, 21 Jun 2023 06:21:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41100 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231324AbjFUKVB (ORCPT ); Wed, 21 Jun 2023 06:21:01 -0400 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33F1710D2 for ; Wed, 21 Jun 2023 03:20:56 -0700 (PDT) Received: by mail-pl1-x632.google.com with SMTP id d9443c01a7336-1b51780bed0so45417425ad.3 for ; Wed, 21 Jun 2023 03:20:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1687342855; x=1689934855; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=QMULsX7Dfo5b2zc6PeXXiTXS5XgNxl2nI88lUF+EMtE=; b=hNhaYwhGaP6KI5AaWtX45Uvo6vzdGw+3RgvM2Pc6af5WTt9Xk8YdtgCjYKK1UMfHeO yQZK/ZDfzszD04HEUinydZdKL3xmCg1x5aBYvETc92RxTf3MkKIZXvBvK5u5iUztQWeq AYVf4tlKpqLY5z/5NWWp0z7QyCYO52BLZ2hNw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687342855; x=1689934855; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=QMULsX7Dfo5b2zc6PeXXiTXS5XgNxl2nI88lUF+EMtE=; b=KFs9xz4Oh3wYt0CGacfcsglmsEfOCTlzulW04Vb7qSZrQ0+zsyScxJTcSdXUlRIYu+ N9VrCWOWARMZD7SVRhbMscRfvivZQ/cUWLc+VrZ90cXog/unkizNM2srrC90dC6yxjMT PswzksJYCTmWAmU+yl4yfYfPzvxIBArJl6yCF9ALm5kNR2AJd7RnoiK5ZPpu6zla3xG2 MZb3jLdVdxWymgh1DDvJJ4tM+JMCZ/5QTGimj3uxdZSBiock35PcoSYScO76baImeRGJ mNz3gW38hFLID9kVN0vCb2eZtrjXrFiAZcpeEWL0VzcNMHQe6N6NJ1pvqW0UzYTSVyjL uarw== X-Gm-Message-State: AC+VfDwjk4buPHMYSv5vEzh8ZbbgLdjPMzvXp7+ICHSxLLEDD/4IuzXh 3xXXJujsE5rVcGmCe6pPB3eOCR34vp9DGcpY7f6cdA== X-Google-Smtp-Source: ACHHUZ7/hNmsWRlrLpNbsJMKJIlg32nbmO1VWpWps6k5fEFwklcOENmUGp7zDOpHSwgP1dAkb1bR7mrJpnwtVIXnF5I= X-Received: by 2002:a17:90a:d811:b0:256:87f4:432a with SMTP id a17-20020a17090ad81100b0025687f4432amr14607505pjv.18.1687342855601; Wed, 21 Jun 2023 03:20:55 -0700 (PDT) MIME-Version: 1.0 References: <20230615152918.3484699-1-revest@chromium.org> In-Reply-To: From: Florent Revest Date: Wed, 21 Jun 2023 12:20:44 +0200 Message-ID: Subject: Re: [PATCH nf] netfilter: conntrack: Avoid nf_ct_helper_hash uses after free To: Pablo Neira Ayuso Cc: netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kadlec@netfilter.org, fw@strlen.de, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, lirongqing@baidu.com, wangli39@baidu.com, zhangyu31@baidu.com, daniel@iogearbox.net, ast@kernel.org, kpsingh@kernel.org, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Tue, Jun 20, 2023 at 8:35=E2=80=AFAM Pablo Neira Ayuso wrote: > > On Thu, Jun 15, 2023 at 05:29:18PM +0200, Florent Revest wrote: > > If register_nf_conntrack_bpf() fails (for example, if the .BTF section > > contains an invalid entry), nf_conntrack_init_start() calls > > nf_conntrack_helper_fini() as part of its cleanup path and > > nf_ct_helper_hash gets freed. > > > > Further netfilter modules like netfilter_conntrack_ftp don't check > > whether nf_conntrack initialized correctly and call > > nf_conntrack_helpers_register() which accesses the freed > > nf_ct_helper_hash and causes a uaf. > > > > This patch guards nf_conntrack_helper_register() from accessing > > freed/uninitialized nf_ct_helper_hash maps and fixes a boot-time > > use-after-free. > > How could this possibly happen? Here is one way to reproduce this bug: # Use nf/main git clone git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf.git cd nf # Start from a minimal config make LLVM=3D1 LLVM_IAS=3D0 defconfig # Enable KASAN, BTF and nf_conntrack_ftp scripts/config -e KASAN -e BPF_SYSCALL -e DEBUG_INFO -e DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT -e DEBUG_INFO_BTF -e NF_CONNTRACK_FTP make LLVM=3D1 LLVM_IAS=3D0 olddefconfig # Build without the LLVM integrated assembler make LLVM=3D1 LLVM_IAS=3D0 -j `nproc` (Note that the use of LLVM_IAS=3D0, KASAN and BTF is just to trigger a bug in BTF that will be fixed by https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=3D97= 24160b3942b0a967b91a59f81da5593f28b8ba Independently of that specific BTF bug, it shows how an error in nf_conntrack_bpf can cause a boot-time uaf in netfilter) Then, booting gives me: [ 4.624666] BPF: [13893] FUNC asan.module_ctor [ 4.625611] BPF: type_id=3D1 [ 4.626176] BPF: [ 4.626601] BPF: Invalid name [ 4.627208] BPF: [ 4.627723] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D [ 4.628610] BUG: KASAN: slab-use-after-free in nf_conntrack_helper_register+0x129/0x2f0 [ 4.628610] Read of size 8 at addr ffff888102d24000 by task swapper/0/1 [ 4.628610] [ 4.628610] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.4.0-rc4-00244-gab39b113e747 #47 [ 4.628610] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-debian-1.16.0-5 04/01/2014 [ 4.628610] Call Trace: [ 4.628610] [ 4.636584] i801_smbus 0000:00:1f.3: SMBus using PCI interrupt [ 4.628610] dump_stack_lvl+0x97/0xd0 [ 4.638738] i2c i2c-0: 1/1 memory slots populated (from DMI) [ 4.628610] print_report+0x17e/0x570 [ 4.640118] i2c i2c-0: Memory type 0x07 not supported yet, not instantiating SPD [ 4.628610] ? __virt_addr_valid+0xe4/0x160 [ 4.628610] kasan_report+0x169/0x1a0 [ 4.628610] ? nf_conntrack_helper_register+0x129/0x2f0 [ 4.628610] nf_conntrack_helper_register+0x129/0x2f0 [ 4.628610] nf_conntrack_helpers_register+0x24/0x60 [ 4.628610] nf_conntrack_ftp_init+0x114/0x140 [ 4.628610] ? __pfx_nf_conntrack_ftp_init+0x10/0x10 [ 4.628610] do_one_initcall+0xe6/0x310 [ 4.628610] ? kasan_set_track+0x61/0x80 [ 4.628610] ? kasan_set_track+0x4f/0x80 [ 4.628610] ? __kasan_kmalloc+0x72/0x90 [ 4.628610] ? __kmalloc+0xa7/0x1a0 [ 4.628610] ? do_initcalls+0x1b/0x70 [ 4.628610] ? kernel_init_freeable+0x174/0x1e0 [ 4.628610] ? kernel_init+0x18/0x1b0 [ 4.628610] ? ret_from_fork+0x29/0x50 [ 4.628610] ? sysvec_apic_timer_interrupt+0xe/0x80 [ 4.628610] ? asm_sysvec_apic_timer_interrupt+0x1a/0x20 [ 4.628610] ? __pfx_ignore_unknown_bootoption+0x10/0x10 [ 4.628610] ? next_arg+0x20b/0x250 [ 4.628610] ? strlen+0x21/0x40 [ 4.628610] ? parse_args+0xc7/0x5f0 [ 4.628610] do_initcall_level+0xa6/0x140 [ 4.628610] do_initcalls+0x3e/0x70 [ 4.628610] kernel_init_freeable+0x174/0x1e0 [ 4.628610] ? __pfx_kernel_init+0x10/0x10 [ 4.628610] kernel_init+0x18/0x1b0 [ 4.628610] ? __pfx_kernel_init+0x10/0x10 [ 4.628610] ret_from_fork+0x29/0x50 [ 4.628610] [ 4.628610] [ 4.628610] Allocated by task 1: [ 4.628610] kasan_set_track+0x4f/0x80 [ 4.628610] __kasan_kmalloc+0x72/0x90 [ 4.628610] __kmalloc_node+0xa7/0x190 [ 4.628610] kvmalloc_node+0x44/0x120 [ 4.628610] nf_ct_alloc_hashtable+0x5b/0xe0 [ 4.628610] nf_conntrack_helper_init+0x1f/0x60 [ 4.628610] nf_conntrack_init_start+0x1c9/0x2d0 [ 4.628610] nf_conntrack_standalone_init+0xb/0xa0 [ 4.628610] do_one_initcall+0xe6/0x310 [ 4.628610] do_initcall_level+0xa6/0x140 [ 4.628610] do_initcalls+0x3e/0x70 [ 4.628610] kernel_init_freeable+0x174/0x1e0 [ 4.628610] kernel_init+0x18/0x1b0 [ 4.628610] ret_from_fork+0x29/0x50 [ 4.628610] [ 4.628610] Freed by task 1: [ 4.628610] kasan_set_track+0x4f/0x80 [ 4.628610] kasan_save_free_info+0x2b/0x50 [ 4.628610] ____kasan_slab_free+0x116/0x1a0 [ 4.628610] __kmem_cache_free+0xc4/0x200 [ 4.628610] nf_conntrack_init_start+0x29c/0x2d0 [ 4.628610] nf_conntrack_standalone_init+0xb/0xa0 [ 4.628610] do_one_initcall+0xe6/0x310 [ 4.628610] do_initcall_level+0xa6/0x140 [ 4.628610] do_initcalls+0x3e/0x70 [ 4.628610] kernel_init_freeable+0x174/0x1e0 [ 4.628610] kernel_init+0x18/0x1b0 [ 4.628610] ret_from_fork+0x29/0x50 [ 4.628610] [ 4.628610] The buggy address belongs to the object at ffff888102d24000 [ 4.628610] which belongs to the cache kmalloc-4k of size 4096 [ 4.628610] The buggy address is located 0 bytes inside of [ 4.628610] freed 4096-byte region [ffff888102d24000, ffff888102d25000) [ 4.628610] [ 4.628610] The buggy address belongs to the physical page: [ 4.628610] page:000000001eb64ba1 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x102d20 [ 4.628610] head:000000001eb64ba1 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0 [ 4.628610] flags: 0x200000000010200(slab|head|node=3D0|zone=3D2) [ 4.628610] page_type: 0xffffffff() [ 4.628610] raw: 0200000000010200 ffff888100043040 dead000000000122 0000000000000000 [ 4.628610] raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000 [ 4.628610] page dumped because: kasan: bad access detected ... > nf_conntrack_ftp depends on nf_conntrack. > > If nf_conntrack fails to load, how can nf_conntrack_ftp be loaded? Is this maybe only true of dynamically loaded kmods ? With CONFIG_NF_CONNTRACK_FTP=3Dy, it seems to me that nf_conntrack_ftp_init() will be called as an __init function, independently of whether nf_conntrack_init_start() succeeded or not. Am I missing something ?