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=-13.0 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 autolearn=unavailable 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 C8377C07E96 for ; Thu, 8 Jul 2021 21:38:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7FFE61439 for ; Thu, 8 Jul 2021 21:38:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231340AbhGHVlW (ORCPT ); Thu, 8 Jul 2021 17:41:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60476 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231285AbhGHVlV (ORCPT ); Thu, 8 Jul 2021 17:41:21 -0400 Received: from mail-yb1-xb31.google.com (mail-yb1-xb31.google.com [IPv6:2607:f8b0:4864:20::b31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8235C061574; Thu, 8 Jul 2021 14:38:38 -0700 (PDT) Received: by mail-yb1-xb31.google.com with SMTP id x192so11321564ybe.6; Thu, 08 Jul 2021 14:38:38 -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=x43n+LTJaTzuRg6vjxk7HVx1IzEgyzJYcKdqMBWkryM=; b=f1W9NHTe36naPmUgZykh2tpD8/AV2expJqlFHrYVxi2CXjNqTZr3VoeHgDTOk0ZtTM y9e2Kn8j6eKTqGLqcElU5tMaFKVRCuKecXdwRyWeOQu1ANQ97E8BBVknUYAmx2oWMntQ tvZh6HbV0TuV/LumHPDu4OXv9KSbjGKzROLGltzzWWLmuNUZblpfs7ULNN+00L80wx44 r3RKvepNE45tKD2keoLO9pzgPCWvoikCic/YJDG7P7R2Vc2V7iGSKDM+0DmAFBmald+f 4SEwXDp+VmBq4MuNQ+L0kDK7s9RDrZ8Jb35Dd/N6ATM97IoBddtqbbHi3rOLk6oA4KqV Dmjg== 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=x43n+LTJaTzuRg6vjxk7HVx1IzEgyzJYcKdqMBWkryM=; b=G9p0hk42Z4/sTW2CdzUvKtf5FuSl13hQzjcApf1au6/VI/gg3f063uF2twLWnWTCIe 4KjCraUbcYjUo1fLWviiKl8VAQUh5D75WtV8XZvkPkX41Ma3nOthZZH0u7VPU2mhn0Zq 12W+BTcRolXCjsxQYqOMqedCw+C6pRytsEYKKO0QFtbGd0TZYOhT1RGY8aJHLjy1v5MP 13EyoGUJd548qiR8aPqtIoiNC5Ne1JZR1Oiw7JL3ZwdcDzLnGDyC7AblzlXyng1qy6XF O8y9HkKZYZNTQZLhOkxSahyMIFWPmW8Nx9RF/RhYrvCWL7AtLzylbYwyVX/+/ro4WyqO CtUA== X-Gm-Message-State: AOAM530a22SjywH/cYAZbsHRq0zS2JIjsFjRVHqSql4GRVvyke0LxqsI OYX7Ou0FJHRYrGDIJu1804/cy8vDIS37/4Kktf7QtxjuuGIg5g== X-Google-Smtp-Source: ABdhPJwMYkLHsmwA2ZnL9euU+6VEkigkMH3ir/kCtnAXyqwym4UO3aBD7qcj1Oh4wBuwEIZUFI/Q89Mg0RIcW0j/puw= X-Received: by 2002:a25:9942:: with SMTP id n2mr42443384ybo.230.1625780317993; Thu, 08 Jul 2021 14:38:37 -0700 (PDT) MIME-Version: 1.0 References: <20210708080532.74526-1-xuanzhuo@linux.alibaba.com> In-Reply-To: <20210708080532.74526-1-xuanzhuo@linux.alibaba.com> From: Andrii Nakryiko Date: Thu, 8 Jul 2021 14:38:26 -0700 Message-ID: Subject: Re: [PATCH net] xdp, net: fix use-after-free in bpf_xdp_link_release To: Xuan Zhuo Cc: Networking , "David S. Miller" , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Eric Dumazet , Antoine Tenart , Alexander Lobakin , Wei Wang , Taehee Yoo , bpf , Abaci , Dust Li Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Jul 8, 2021 at 1:05 AM Xuan Zhuo wrote: > > The problem occurs between dev_get_by_index() and dev_xdp_attach_link(). > At this point in time, the xdp link will not be released automatically > when dev is deleted. In this way, when xdp link is released, dev will > still be accessed, but dev has been released. Do I understand correctly that the problem is that between when get dev with dev_get_by_index() and by the time we call dev_xdp_attach_link() to record bpf_link inside dev we might get a call to dev_xdp_uninstall(dev). At that point we missed the notification that dev is going away but we still succeed to attach bpf_link. Do I understand the situation correctly? If yes, I wonder whether the proper fix would be to make sure that if the device was removed bpf_xdp_link_attach() will return an error. That seems like a sane behavior, instead of pretending that attachment succeeded. At that point we should NULL out link->dev and cleanup bpf_xdp_link. > > [ 45.966867] BUG: KASAN: use-after-free in bpf_xdp_link_release+0x3b8/0x3d0 > [ 45.967619] Read of size 8 at addr ffff00000f9980c8 by task a.out/732 > [ 45.968297] > [ 45.968502] CPU: 1 PID: 732 Comm: a.out Not tainted 5.13.0+ #22 > [ 45.969222] Hardware name: linux,dummy-virt (DT) > [ 45.969795] Call trace: > [ 45.970106] dump_backtrace+0x0/0x4c8 > [ 45.970564] show_stack+0x30/0x40 > [ 45.970981] dump_stack_lvl+0x120/0x18c > [ 45.971470] print_address_description.constprop.0+0x74/0x30c > [ 45.972182] kasan_report+0x1e8/0x200 > [ 45.972659] __asan_report_load8_noabort+0x2c/0x50 > [ 45.973273] bpf_xdp_link_release+0x3b8/0x3d0 > [ 45.973834] bpf_link_free+0xd0/0x188 > [ 45.974315] bpf_link_put+0x1d0/0x218 > [ 45.974790] bpf_link_release+0x3c/0x58 > [ 45.975291] __fput+0x20c/0x7e8 > [ 45.975706] ____fput+0x24/0x30 > [ 45.976117] task_work_run+0x104/0x258 > [ 45.976609] do_notify_resume+0x894/0xaf8 > [ 45.977121] work_pending+0xc/0x328 > [ 45.977575] > [ 45.977775] The buggy address belongs to the page: > [ 45.978369] page:fffffc00003e6600 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4f998 > [ 45.979522] flags: 0x7fffe0000000000(node=0|zone=0|lastcpupid=0x3ffff) > [ 45.980349] raw: 07fffe0000000000 fffffc00003e6708 ffff0000dac3c010 0000000000000000 > [ 45.981309] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 > [ 45.982259] page dumped because: kasan: bad access detected > [ 45.982948] > [ 45.983153] Memory state around the buggy address: > [ 45.983753] ffff00000f997f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > [ 45.984645] ffff00000f998000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > [ 45.985533] >ffff00000f998080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > [ 45.986419] ^ > [ 45.987112] ffff00000f998100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > [ 45.988006] ffff00000f998180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > [ 45.988895] ================================================================== > [ 45.989773] Disabling lock debugging due to kernel taint > [ 45.990552] Kernel panic - not syncing: panic_on_warn set ... > [ 45.991166] CPU: 1 PID: 732 Comm: a.out Tainted: G B 5.13.0+ #22 > [ 45.991929] Hardware name: linux,dummy-virt (DT) > [ 45.992448] Call trace: > [ 45.992753] dump_backtrace+0x0/0x4c8 > [ 45.993208] show_stack+0x30/0x40 > [ 45.993627] dump_stack_lvl+0x120/0x18c > [ 45.994113] dump_stack+0x1c/0x34 > [ 45.994530] panic+0x3a4/0x7d8 > [ 45.994930] end_report+0x194/0x198 > [ 45.995380] kasan_report+0x134/0x200 > [ 45.995850] __asan_report_load8_noabort+0x2c/0x50 > [ 45.996453] bpf_xdp_link_release+0x3b8/0x3d0 > [ 45.997007] bpf_link_free+0xd0/0x188 > [ 45.997474] bpf_link_put+0x1d0/0x218 > [ 45.997942] bpf_link_release+0x3c/0x58 > [ 45.998429] __fput+0x20c/0x7e8 > [ 45.998833] ____fput+0x24/0x30 > [ 45.999247] task_work_run+0x104/0x258 > [ 45.999731] do_notify_resume+0x894/0xaf8 > [ 46.000236] work_pending+0xc/0x328 > [ 46.000697] SMP: stopping secondary CPUs > [ 46.001226] Dumping ftrace buffer: > [ 46.001663] (ftrace buffer empty) > [ 46.002110] Kernel Offset: disabled > [ 46.002545] CPU features: 0x00000001,23202c00 > [ 46.003080] Memory Limit: none > > Reported-by: Abaci > Signed-off-by: Xuan Zhuo > Reviewed-by: Dust Li > --- > net/core/dev.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/net/core/dev.c b/net/core/dev.c > index c253c2aafe97..f7aba3108016 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -9684,14 +9684,17 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) > struct net_device *dev; > int err, fd; > > + rtnl_lock(); > dev = dev_get_by_index(net, attr->link_create.target_ifindex); > - if (!dev) > + if (!dev) { > + rtnl_unlock(); > return -EINVAL; > + } > > link = kzalloc(sizeof(*link), GFP_USER); > if (!link) { > err = -ENOMEM; > - goto out_put_dev; > + goto unlock_put_dev; > } > > bpf_link_init(&link->link, BPF_LINK_TYPE_XDP, &bpf_xdp_link_lops, prog); > @@ -9701,10 +9704,9 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) > err = bpf_link_prime(&link->link, &link_primer); > if (err) { > kfree(link); > - goto out_put_dev; > + goto unlock_put_dev; > } > > - rtnl_lock(); > err = dev_xdp_attach_link(dev, NULL, link); > rtnl_unlock(); > > @@ -9718,6 +9720,9 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) > dev_put(dev); > return fd; > > +unlock_put_dev: > + rtnl_unlock(); > + > out_put_dev: > dev_put(dev); > return err; > -- > 2.31.0 >