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=-12.8 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 502E3C07E9C for ; Mon, 12 Jul 2021 23:22:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 33D866115A for ; Mon, 12 Jul 2021 23:22:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231426AbhGLXZl (ORCPT ); Mon, 12 Jul 2021 19:25:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37678 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230137AbhGLXZj (ORCPT ); Mon, 12 Jul 2021 19:25:39 -0400 Received: from mail-yb1-xb2c.google.com (mail-yb1-xb2c.google.com [IPv6:2607:f8b0:4864:20::b2c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85487C0613DD; Mon, 12 Jul 2021 16:22:49 -0700 (PDT) Received: by mail-yb1-xb2c.google.com with SMTP id b13so31743071ybk.4; Mon, 12 Jul 2021 16:22:49 -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=zQfeDJbiNEXtYkXXzSo9DJBIXTxsz1leGy7dEyIJUI8=; b=S8b2fbMpDAH/i0fTN+NOSpv9UhUm9ieTMyitzYFVrZllSmFh3BXEqoxDn+lC8OAHqC O9fAVzQ56o55TUUEx+Mn0CeiMVUPNyNBczwDmTHsi0ChZS/ROH5tKPaIS9F3iEXnEJFt VYnzjF5HCz4u6SqTLYYwnw4IZbhE9F1nDc87fVcPFLJ09Wt6dUWVosd5UfsDrqs7LrX9 oaAIFB1GDmirW541dh1FMFpZ9dVwijyL0zgHyu5YPXFeDASWq+/gQWs2/9YggXuMzgnp rqPehneNlJ9xyLGdqNmJNRNrjVA8+6qZkKsdrL5tEBFgR9HY2FtDicoblRPBhM0YRIq7 Omrg== 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=zQfeDJbiNEXtYkXXzSo9DJBIXTxsz1leGy7dEyIJUI8=; b=NwXkisn5Df8Hj6FfBvU0V3XnkNOoJak2OYdAtsJIr5YpKUHfojB44fPJFIsPW95X+e N+oRDpHMo/s4qSG3A0I6HYtz9cUOcWxuj08gYGmboRFkVIuv4sPz7hcstV57rmEWJUNM P0rKmBDxg17JugqUHuBrGSxTiJckcq9uRusDpFtv3TJFx9oZkiwiWaLFl4qgw+4ABlBK dcu+SQkGnUIENtQER3K2kQ3u+LuzmlfZtFcqfsuHvXGxOunjUImCCuD1otuXxQqDKnkU IyGAi7d+rrRDk4s3cZHN3hnw0iZtKNlPjsUEGJuAGms7KzLV+qMm8COfqd7xxl3r9Zl9 jaew== X-Gm-Message-State: AOAM533VDNXu6Vp+IVaPcPvrQFc9BVqSSVRkBkjAt+MT1uGn+Ewb81zU BInR4vBk0O7TUR8M8wSFABDz2G8bzoeGdHzyDwK9QKmFdvnHjA== X-Google-Smtp-Source: ABdhPJwhwBW0CyZ0SHfNJc8uRA3mEumLQhCC0G5wEfhirLhfxGVR3x9VrpD+XR2PwaEO4MOwSj43dEz4fYIRzTTb1Us= X-Received: by 2002:a25:bd09:: with SMTP id f9mr1962367ybk.27.1626132168816; Mon, 12 Jul 2021 16:22:48 -0700 (PDT) MIME-Version: 1.0 References: <20210710031635.41649-1-xuanzhuo@linux.alibaba.com> In-Reply-To: <20210710031635.41649-1-xuanzhuo@linux.alibaba.com> From: Andrii Nakryiko Date: Mon, 12 Jul 2021 16:22:37 -0700 Message-ID: Subject: Re: [PATCH net v4] 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: netdev@vger.kernel.org On Fri, Jul 9, 2021 at 8:16 PM Xuan Zhuo wrote: > > The problem occurs between dev_get_by_index() and dev_xdp_attach_link(). > At this point, dev_xdp_uninstall() is called. Then xdp link will not be > detached automatically when dev is released. But link->dev already > points to dev, when xdp link is released, dev will still be accessed, > but dev has been released. > > dev_get_by_index() | > link->dev = dev | > | rtnl_lock() > | unregister_netdevice_many() > | dev_xdp_uninstall() > | rtnl_unlock() > rtnl_lock(); | > dev_xdp_attach_link() | > rtnl_unlock(); | > | netdev_run_todo() // dev released > bpf_xdp_link_release() | > /* access dev. | > use-after-free */ | > > [ 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 > > Fixes: aa8d3a716b59db6c ("bpf, xdp: Add bpf_link-based XDP attachment API") > Reported-by: Abaci > Signed-off-by: Xuan Zhuo > Reviewed-by: Dust Li > --- LGTM, thanks for the fix! Acked-by: Andrii Nakryiko > > v4: fix commit message > > v3: v1 + "link->dev = NULL" > > net/core/dev.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/net/core/dev.c b/net/core/dev.c > index c253c2aafe97..9f508c597037 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; > } > > bpf_link_init(&link->link, BPF_LINK_TYPE_XDP, &bpf_xdp_link_lops, prog); > @@ -9701,14 +9704,14 @@ 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; > } > > - rtnl_lock(); > err = dev_xdp_attach_link(dev, NULL, link); > rtnl_unlock(); > > if (err) { > + link->dev = NULL; > bpf_link_cleanup(&link_primer); > goto out_put_dev; > } > @@ -9718,6 +9721,9 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) > dev_put(dev); > return fd; > > +unlock: > + rtnl_unlock(); > + > out_put_dev: > dev_put(dev); > return err; > -- > 2.31.0 >