KASAN: use-after-free Write in hiddev_disconnect

KASAN: use-after-free Write in hiddev_disconnect

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    5a67532c usb: gadget: add raw-gadget interface
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=10b1419ee00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9ba75825443d54bd
dashboard link: https://syzkaller.appspot.com/bug?extid=784ccb935f9900cc7c9e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+784ccb935f9900cc7c9e@syzkaller.appspotmail.com

usb 6-1: USB disconnect, device number 34
==================================================================
BUG: KASAN: use-after-free in register_lock_class+0xeda/0x11d0  
kernel/locking/lockdep.c:1263
Write of size 8 at addr ffff8881ce6284b0 by task kworker/0:3/3833

CPU: 0 PID: 3833 Comm: kworker/0:3 Not tainted 5.5.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: usb_hub_wq hub_event
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0xef/0x16e lib/dump_stack.c:118
  print_address_description.constprop.0.cold+0xd3/0x314 mm/kasan/report.c:374
  __kasan_report.cold+0x37/0x85 mm/kasan/report.c:506
  kasan_report+0xe/0x20 mm/kasan/common.c:639
  register_lock_class+0xeda/0x11d0 kernel/locking/lockdep.c:1263
  __lock_acquire+0xfc/0x3b60 kernel/locking/lockdep.c:3837
  lock_acquire+0x130/0x340 kernel/locking/lockdep.c:4485
  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
  _raw_spin_lock_irqsave+0x32/0x50 kernel/locking/spinlock.c:159
  __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:122
  hiddev_disconnect+0x154/0x1b4 drivers/hid/usbhid/hiddev.c:937
  hid_disconnect+0xb4/0x1a0 drivers/hid/hid-core.c:2008
  hid_hw_stop+0x12/0x70 drivers/hid/hid-core.c:2053
  cmhid_remove+0x38/0x50 drivers/hid/hid-cmedia.c:140
  hid_device_remove+0xed/0x240 drivers/hid/hid-core.c:2294
  __device_release_driver drivers/base/dd.c:1132 [inline]
  device_release_driver_internal+0x231/0x500 drivers/base/dd.c:1165
  bus_remove_device+0x2eb/0x5a0 drivers/base/bus.c:532
  device_del+0x481/0xd30 drivers/base/core.c:2664
  hid_remove_device drivers/hid/hid-core.c:2465 [inline]
  hid_destroy_device+0xe1/0x150 drivers/hid/hid-core.c:2484
  usbhid_disconnect+0x9f/0xe0 drivers/hid/usbhid/hid-core.c:1413
  usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:423
  __device_release_driver drivers/base/dd.c:1134 [inline]
  device_release_driver_internal+0x42f/0x500 drivers/base/dd.c:1165
  bus_remove_device+0x2eb/0x5a0 drivers/base/bus.c:532
  device_del+0x481/0xd30 drivers/base/core.c:2664
  usb_disable_device+0x23d/0x790 drivers/usb/core/message.c:1237
  usb_disconnect+0x293/0x900 drivers/usb/core/hub.c:2200
  hub_port_connect drivers/usb/core/hub.c:5035 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5324 [inline]
  port_event drivers/usb/core/hub.c:5470 [inline]
  hub_event+0x1a1d/0x4300 drivers/usb/core/hub.c:5552
  process_one_work+0x945/0x15c0 kernel/workqueue.c:2264
  worker_thread+0x96/0xe20 kernel/workqueue.c:2410
  kthread+0x318/0x420 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 5:
  save_stack+0x1b/0x80 mm/kasan/common.c:72
  set_track mm/kasan/common.c:80 [inline]
  __kasan_kmalloc mm/kasan/common.c:513 [inline]
  __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:486
  kmalloc include/linux/slab.h:556 [inline]
  kzalloc include/linux/slab.h:670 [inline]
  hiddev_connect+0x242/0x5b0 drivers/hid/usbhid/hiddev.c:890
  hid_connect+0x239/0xbb0 drivers/hid/hid-core.c:1934
  hid_hw_start drivers/hid/hid-core.c:2033 [inline]
  hid_hw_start+0xa2/0x130 drivers/hid/hid-core.c:2024
  cmhid_probe+0x104/0x160 drivers/hid/hid-cmedia.c:123
  hid_device_probe+0x2be/0x3f0 drivers/hid/hid-core.c:2261
  really_probe+0x290/0xad0 drivers/base/dd.c:548
  driver_probe_device+0x223/0x350 drivers/base/dd.c:721
  __device_attach_driver+0x1d1/0x290 drivers/base/dd.c:828
  bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
  __device_attach+0x217/0x390 drivers/base/dd.c:894
  bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
  device_add+0x1459/0x1bf0 drivers/base/core.c:2487
  hid_add_device drivers/hid/hid-core.c:2417 [inline]
  hid_add_device+0x33c/0x9a0 drivers/hid/hid-core.c:2366
  usbhid_probe+0xa81/0xfa0 drivers/hid/usbhid/hid-core.c:1386
  usb_probe_interface+0x310/0x800 drivers/usb/core/driver.c:361
  really_probe+0x290/0xad0 drivers/base/dd.c:548
  driver_probe_device+0x223/0x350 drivers/base/dd.c:721
  __device_attach_driver+0x1d1/0x290 drivers/base/dd.c:828
  bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
  __device_attach+0x217/0x390 drivers/base/dd.c:894
  bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
  device_add+0x1459/0x1bf0 drivers/base/core.c:2487
  usb_set_configuration+0xe47/0x17d0 drivers/usb/core/message.c:2023
  generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
  usb_probe_device+0xaf/0x140 drivers/usb/core/driver.c:266
  really_probe+0x290/0xad0 drivers/base/dd.c:548
  driver_probe_device+0x223/0x350 drivers/base/dd.c:721
  __device_attach_driver+0x1d1/0x290 drivers/base/dd.c:828
  bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:430
  __device_attach+0x217/0x390 drivers/base/dd.c:894
  bus_probe_device+0x1e4/0x290 drivers/base/bus.c:490
  device_add+0x1459/0x1bf0 drivers/base/core.c:2487
  usb_new_device.cold+0x540/0xcd0 drivers/usb/core/hub.c:2537
  hub_port_connect drivers/usb/core/hub.c:5184 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5324 [inline]
  port_event drivers/usb/core/hub.c:5470 [inline]
  hub_event+0x21cb/0x4300 drivers/usb/core/hub.c:5552
  process_one_work+0x945/0x15c0 kernel/workqueue.c:2264
  worker_thread+0x96/0xe20 kernel/workqueue.c:2410
  kthread+0x318/0x420 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Freed by task 4638:
  save_stack+0x1b/0x80 mm/kasan/common.c:72
  set_track mm/kasan/common.c:80 [inline]
  kasan_set_free_info mm/kasan/common.c:335 [inline]
  __kasan_slab_free+0x117/0x160 mm/kasan/common.c:474
  slab_free_hook mm/slub.c:1425 [inline]
  slab_free_freelist_hook mm/slub.c:1458 [inline]
  slab_free mm/slub.c:3005 [inline]
  kfree+0xd5/0x300 mm/slub.c:3957
  hiddev_release+0x402/0x520 drivers/hid/usbhid/hiddev.c:232
  __fput+0x2d7/0x840 fs/file_table.c:280
  task_work_run+0x13f/0x1c0 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0xb8b/0x2c50 kernel/exit.c:801
  do_group_exit+0x125/0x340 kernel/exit.c:899
  get_signal+0x480/0x2470 kernel/signal.c:2734
  do_signal+0x88/0x1490 arch/x86/kernel/signal.c:815
  exit_to_usermode_loop+0x1a2/0x200 arch/x86/entry/common.c:160
  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
  do_syscall_64+0x4e0/0x5a0 arch/x86/entry/common.c:304
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881ce628400
  which belongs to the cache kmalloc-512 of size 512
The buggy address is located 176 bytes inside of
  512-byte region [ffff8881ce628400, ffff8881ce628600)
The buggy address belongs to the page:
page:ffffea0007398a00 refcount:1 mapcount:0 mapping:ffff8881da002500  
index:0xffff8881ce62a800 compound_mapcount: 0
raw: 0200000000010200 0000000000000000 0000000100000001 ffff8881da002500
raw: ffff8881ce62a800 000000008010000f 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8881ce628380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
  ffff8881ce628400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881ce628480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                      ^
  ffff8881ce628500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8881ce628580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
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Re: KASAN: use-after-free Write in hiddev_disconnect

[Dan Carpenter]

I'm trying to take a stab at diagnosing these bugs.  (But I'm seldom
smart enough to actually fix anything).  These hiddev_disconnect() bugs
are a race condition:

devel/drivers/hid/usbhid/hiddev.c
   924  void hiddev_disconnect(struct hid_device *hid)
   925  {
   926          struct hiddev *hiddev = hid->hiddev;
   927          struct usbhid_device *usbhid = hid->driver_data;
   928  
   929          usb_deregister_dev(usbhid->intf, &hiddev_class);
   930  
   931          mutex_lock(&hiddev->existancelock);
   932          hiddev->exist = 0;
                ^^^^^^^^^^^^^^^^^^
We set "exist = 0;"

   933  
   934          if (hiddev->open) {
   935                  mutex_unlock(&hiddev->existancelock);
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Then we drop the lock.

   936                  hid_hw_close(hiddev->hid);
   937                  wake_up_interruptible(&hiddev->wait);
                                               ^^^^^^
The other thread frees hiddev and it crashes here.

   938          } else {
   939                  mutex_unlock(&hiddev->existancelock);
   940                  kfree(hiddev);
   941          }
   942  }

The other thread is doing:

drivers/hid/usbhid/hiddev.c
   216  static int hiddev_release(struct inode * inode, struct file * file)
   217  {
   218          struct hiddev_list *list = file->private_data;
   219          unsigned long flags;
   220  
   221          spin_lock_irqsave(&list->hiddev->list_lock, flags);
   222          list_del(&list->node);
   223          spin_unlock_irqrestore(&list->hiddev->list_lock, flags);
   224  
   225          mutex_lock(&list->hiddev->existancelock);
                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^
Takes the lock.

   226          if (!--list->hiddev->open) {
                     ^^^^^^^^^^^^^^^^^^^^
Decrements open.

   227                  if (list->hiddev->exist) {
                            ^^^^^^^^^^^^^^^^^^^
This is false.

   228                          hid_hw_close(list->hiddev->hid);
   229                          hid_hw_power(list->hiddev->hid, PM_HINT_NORMAL);
   230                  } else {
   231                          mutex_unlock(&list->hiddev->existancelock);
   232                          kfree(list->hiddev);
                                      ^^^^^^^^^^^^
Freed here.

   233                          vfree(list);
   234                          return 0;
   235                  }
   236          }
   237  
   238          mutex_unlock(&list->hiddev->existancelock);
   239          vfree(list);
   240  
   241          return 0;
   242  }

I'm not sure what the fix should be though.

regards,
dan carpenter

Re: KASAN: use-after-free Write in hiddev_disconnect

[Alan Stern]

On Tue, 14 Jan 2020, Dan Carpenter wrote:

> I'm trying to take a stab at diagnosing these bugs.  (But I'm seldom
> smart enough to actually fix anything).  These hiddev_disconnect() bugs
> are a race condition:
> 
> devel/drivers/hid/usbhid/hiddev.c
>    924  void hiddev_disconnect(struct hid_device *hid)
>    925  {
>    926          struct hiddev *hiddev = hid->hiddev;
>    927          struct usbhid_device *usbhid = hid->driver_data;
>    928  
>    929          usb_deregister_dev(usbhid->intf, &hiddev_class);
>    930  
>    931          mutex_lock(&hiddev->existancelock);
>    932          hiddev->exist = 0;
>                 ^^^^^^^^^^^^^^^^^^
> We set "exist = 0;"
> 
>    933  
>    934          if (hiddev->open) {
>    935                  mutex_unlock(&hiddev->existancelock);
>                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Then we drop the lock.
> 
>    936                  hid_hw_close(hiddev->hid);
>    937                  wake_up_interruptible(&hiddev->wait);
>                                                ^^^^^^
> The other thread frees hiddev and it crashes here.
> 
>    938          } else {
>    939                  mutex_unlock(&hiddev->existancelock);
>    940                  kfree(hiddev);
>    941          }
>    942  }
> 
> The other thread is doing:
> 
> drivers/hid/usbhid/hiddev.c
>    216  static int hiddev_release(struct inode * inode, struct file * file)
>    217  {
>    218          struct hiddev_list *list = file->private_data;
>    219          unsigned long flags;
>    220  
>    221          spin_lock_irqsave(&list->hiddev->list_lock, flags);
>    222          list_del(&list->node);
>    223          spin_unlock_irqrestore(&list->hiddev->list_lock, flags);
>    224  
>    225          mutex_lock(&list->hiddev->existancelock);
>                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Takes the lock.
> 
>    226          if (!--list->hiddev->open) {
>                      ^^^^^^^^^^^^^^^^^^^^
> Decrements open.
> 
>    227                  if (list->hiddev->exist) {
>                             ^^^^^^^^^^^^^^^^^^^
> This is false.
> 
>    228                          hid_hw_close(list->hiddev->hid);
>    229                          hid_hw_power(list->hiddev->hid, PM_HINT_NORMAL);
>    230                  } else {
>    231                          mutex_unlock(&list->hiddev->existancelock);
>    232                          kfree(list->hiddev);
>                                       ^^^^^^^^^^^^
> Freed here.
> 
>    233                          vfree(list);
>    234                          return 0;
>    235                  }
>    236          }
>    237  
>    238          mutex_unlock(&list->hiddev->existancelock);
>    239          vfree(list);
>    240  
>    241          return 0;
>    242  }
> 
> I'm not sure what the fix should be though.

Good sleuthing!

It certainly looks as though hiddev_disconnect() should not try to
reference hiddev after dropping the existance_lock -- at least, not in
the case that the device file is still open.  So I suggest reordering
the statements in that routine: First call hid_hw_close() and
wake_up_interruptible(), then drop the mutex.

Too bad syzbot doesn't have a reproducer to test this, though.

Alan Stern

[PATCH] HID: hiddev: Fix race in in hiddev_disconnect()

[Dan Carpenter, syzbot]

Syzbot reports that "hiddev" is used after it's free in hiddev_disconnect().
The hiddev_disconnect() function sets "hiddev->exist = 0;" so
hiddev_release() can free it as soon as we drop the "existancelock"
lock.  This patch moves the mutex_unlock(&hiddev->existancelock) until
after we have finished using it.

Reported-by: syzbot+784ccb935f9900cc7c9e@syzkaller.appspotmail.com
Fixes: 7f77897ef2b6 ("HID: hiddev: fix potential use-after-free")
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 drivers/hid/usbhid/hiddev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index a970b809d778..4140dea693e9 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -932,9 +932,9 @@ void hiddev_disconnect(struct hid_device *hid)
 	hiddev->exist = 0;
 
 	if (hiddev->open) {
-		mutex_unlock(&hiddev->existancelock);
 		hid_hw_close(hiddev->hid);
 		wake_up_interruptible(&hiddev->wait);
+		mutex_unlock(&hiddev->existancelock);
 	} else {
 		mutex_unlock(&hiddev->existancelock);
 		kfree(hiddev);
-- 
2.11.0

Re: [PATCH] HID: hiddev: Fix race in in hiddev_disconnect()

[Jiri Kosina]

On Wed, 15 Jan 2020, Dan Carpenter wrote:

> Syzbot reports that "hiddev" is used after it's free in hiddev_disconnect().
> The hiddev_disconnect() function sets "hiddev->exist = 0;" so
> hiddev_release() can free it as soon as we drop the "existancelock"
> lock.  This patch moves the mutex_unlock(&hiddev->existancelock) until
> after we have finished using it.
> 
> Reported-by: syzbot+784ccb935f9900cc7c9e@syzkaller.appspotmail.com
> Fixes: 7f77897ef2b6 ("HID: hiddev: fix potential use-after-free")
> Suggested-by: Alan Stern <stern@rowland.harvard.edu>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Applied to for-5.6/upstream-fixes. Thanks,

-- 
Jiri Kosina
SUSE Labs