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 X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D67E3C12002 for ; Fri, 16 Jul 2021 20:44:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B87DB613F8 for ; Fri, 16 Jul 2021 20:44:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230353AbhGPUrC (ORCPT ); Fri, 16 Jul 2021 16:47:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42898 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230256AbhGPUrC (ORCPT ); Fri, 16 Jul 2021 16:47:02 -0400 Received: from mail-yb1-xb35.google.com (mail-yb1-xb35.google.com [IPv6:2607:f8b0:4864:20::b35]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EBF39C06175F; Fri, 16 Jul 2021 13:44:06 -0700 (PDT) Received: by mail-yb1-xb35.google.com with SMTP id g5so16866798ybu.10; Fri, 16 Jul 2021 13:44:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=q2gswAbNH1obxNTNlaEj+a8poBJQn9ocu7cMCkTxcXc=; b=VcxqbuO13iNjgtwhVwNvkefz+rQVovI+bp61MiQyK5nLd9PTReE5ZtM4/4nbgkXg+V EBaMpztGPenFBXKKe28j4WVe3qKwSVJgFySmnFs7JVBrIvVCnaciHSOKC86Mutw0L0QB h7BNu2w1TJlGdah3mZCvWg/pFKdvp1WxEqX3gUjTkzKp9PSaoaMgZ4JuPM1nlPs9SzRA KwAcvRFJcIEIcWXtE1PlSfpJy29XvaXQFU0VHR2PhvMuNS3gdC03H7acFzXpGlPkWOVN HIwW5lxM6RcaEOo0Lx4gSdIxNEAI2uRq1GN12YbjskJDNz40P1pGguq6EP/JbSaZxBHx zhXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=q2gswAbNH1obxNTNlaEj+a8poBJQn9ocu7cMCkTxcXc=; b=RoE4BsKzy76tZX/HxzdGwkgfbHrE9znlkmpR9jJHGNQcDPlt/sUTeMp5hqM0CaD6yy TujV9Fw1B1SpGEkqupCbnOwYduPvUXXCPruO8c0rMxq+m3m0DKGlGCsc4+n5/WC/B8oK 7+g2tytw/bVZla5heiKsHoImQFnh/UT2YJ9HA1RLvVXE7TuLdy9FCH0osZl8kT/otKAc M6Dic+o65GwkVnTR3i3AYVADfhOr3PwKKLYw5zS7mcsmchRgaZxTbzNTTPhvjn4cFUqV Lpy/TAzVNH1l/4970HUNYAcJ7/DaZis7dYaUos8OnXQmNvGpXQOXOPb2x6/SK2p6vh6B j33Q== X-Gm-Message-State: AOAM531Y5haCr/mb5gN/EZqVGlqEjVX8JB2wI9zJ1hpEpymXzUkxNPFM hfxy0RG3DUcMd/uxVrxVHI80G4OLzgdcNl4GqtI= X-Google-Smtp-Source: ABdhPJzq/D0ABJ7rYDRGP6M1PpYDxPBU31zy86XSOPqyhA+HidsNy4qgnJpA+U/0CN3H5WWhDKM40k1OyQUp+AHnzt0= X-Received: by 2002:a25:b203:: with SMTP id i3mr15248038ybj.260.1626468246223; Fri, 16 Jul 2021 13:44:06 -0700 (PDT) MIME-Version: 1.0 References: <20210716100452.113652-1-lmb@cloudflare.com> In-Reply-To: <20210716100452.113652-1-lmb@cloudflare.com> From: Andrii Nakryiko Date: Fri, 16 Jul 2021 13:43:55 -0700 Message-ID: Subject: Re: [PATCH bpf] bpf: fix OOB read when printing XDP link fdinfo To: Lorenz Bauer Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend , kernel-team , Andrii Nakryiko , Networking , bpf , open list Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Jul 16, 2021 at 3:05 AM Lorenz Bauer wrote: > > We got the following UBSAN report on one of our testing machines: > > ================================================================================ > UBSAN: array-index-out-of-bounds in kernel/bpf/syscall.c:2389:24 > index 6 is out of range for type 'char *[6]' > CPU: 43 PID: 930921 Comm: systemd-coredum Tainted: G O 5.10.48-cloudflare-kasan-2021.7.0 #1 > Hardware name: > Call Trace: > dump_stack+0x7d/0xa3 > ubsan_epilogue+0x5/0x40 > __ubsan_handle_out_of_bounds.cold+0x43/0x48 > ? seq_printf+0x17d/0x250 > bpf_link_show_fdinfo+0x329/0x380 > ? bpf_map_value_size+0xe0/0xe0 > ? put_files_struct+0x20/0x2d0 > ? __kasan_kmalloc.constprop.0+0xc2/0xd0 > seq_show+0x3f7/0x540 > seq_read_iter+0x3f8/0x1040 > seq_read+0x329/0x500 > ? seq_read_iter+0x1040/0x1040 > ? __fsnotify_parent+0x80/0x820 > ? __fsnotify_update_child_dentry_flags+0x380/0x380 > vfs_read+0x123/0x460 > ksys_read+0xed/0x1c0 > ? __x64_sys_pwrite64+0x1f0/0x1f0 > do_syscall_64+0x33/0x40 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > ================================================================================ > ================================================================================ > UBSAN: object-size-mismatch in kernel/bpf/syscall.c:2384:2 > > From the report, we can infer that some array access in bpf_link_show_fdinfo at index 6 > is out of bounds. The obvious candidate is bpf_link_type_strs[BPF_LINK_TYPE_XDP] with > BPF_LINK_TYPE_XDP == 6. It turns out that BPF_LINK_TYPE_XDP is missing from bpf_types.h > and therefore doesn't have an entry in bpf_link_type_strs: > > pos: 0 > flags: 02000000 > mnt_id: 13 > link_type: (null) > link_id: 4 > prog_tag: bcf7977d3b93787c > prog_id: 4 > ifindex: 1 > > Fixes: aa8d3a716b59 ("bpf, xdp: Add bpf_link-based XDP attachment API") > Signed-off-by: Lorenz Bauer > --- Well, oops. Thanks for the fix! Acked-by: Andrii Nakryiko It would be great to have a compilation error for something like this. I wonder if we can do something to detect this going forward? > include/linux/bpf_types.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h > index a9db1eae6796..be95f2722ad9 100644 > --- a/include/linux/bpf_types.h > +++ b/include/linux/bpf_types.h > @@ -135,3 +135,4 @@ BPF_LINK_TYPE(BPF_LINK_TYPE_ITER, iter) > #ifdef CONFIG_NET > BPF_LINK_TYPE(BPF_LINK_TYPE_NETNS, netns) > #endif > +BPF_LINK_TYPE(BPF_LINK_TYPE_XDP, xdp) > -- > 2.30.2 >