diff mbox series

[net,v4] xdp, net: fix use-after-free in bpf_xdp_link_release

Message ID 20210710031635.41649-1-xuanzhuo@linux.alibaba.com
State New
Headers show
Series [net,v4] xdp, net: fix use-after-free in bpf_xdp_link_release | expand

Commit Message

Xuan Zhuo July 10, 2021, 3:16 a.m. UTC 
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@linux.alibaba.com>
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
---

v4: fix commit message

v3: v1 + "link->dev = NULL"

 net/core/dev.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

--
2.31.0

Comments

Andrii Nakryiko July 12, 2021, 11:22 p.m. UTC | #1 
On Fri, Jul 9, 2021 at 8:16 PM Xuan Zhuo <xuanzhuo@linux.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@linux.alibaba.com>

> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

> Reviewed-by: Dust Li <dust.li@linux.alibaba.com>

> ---


LGTM, thanks for the fix!

Acked-by: Andrii Nakryiko <andrii@kernel.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

>
Alexei Starovoitov July 13, 2021, 7:04 p.m. UTC | #2 
On Mon, Jul 12, 2021 at 4:22 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>

> On Fri, Jul 9, 2021 at 8:16 PM Xuan Zhuo <xuanzhuo@linux.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@linux.alibaba.com>

> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

> > Reviewed-by: Dust Li <dust.li@linux.alibaba.com>

> > ---

>

> LGTM, thanks for the fix!

>

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


Applied. Thanks
diff mbox series

Patch

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;