lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Mon, 12 Jul 2021 16:22:37 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     Networking <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Antoine Tenart <atenart@...nel.org>,
        Alexander Lobakin <alobakin@...me>,
        Wei Wang <weiwan@...gle.com>, Taehee Yoo <ap420073@...il.com>,
        bpf <bpf@...r.kernel.org>, Abaci <abaci@...ux.alibaba.com>,
        Dust Li <dust.li@...ux.alibaba.com>
Subject: Re: [PATCH net v4] xdp, net: fix use-after-free in bpf_xdp_link_release

On Fri, Jul 9, 2021 at 8:16 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> 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 <abaci@...ux.alibaba.com>
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> Reviewed-by: Dust Li <dust.li@...ux.alibaba.com>
> ---

LGTM, thanks for the fix!

Acked-by: Andrii Nakryiko <andrii@...nel.org>

>
> 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
>

Powered by blists - more mailing lists