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* possible deadlock in usb_deregister_dev (2)
@ 2019-09-16 16:09 syzbot
  2019-09-16 21:42 ` syzbot
       [not found] ` <20190917080119.3940-1-hdanton@sina.com>
  0 siblings, 2 replies; 5+ messages in thread
From: syzbot @ 2019-09-16 16:09 UTC (permalink / raw)
  To: andreyknvl, gregkh, linux-kernel, linux-usb, stern, syzkaller-bugs

Hello,

syzbot found the following crash on:

HEAD commit:    f0df5c1b usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=1742f159600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
dashboard link: https://syzkaller.appspot.com/bug?extid=f9549f5ee8a5416f0b95
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+f9549f5ee8a5416f0b95@syzkaller.appspotmail.com

usb 5-1: USB disconnect, device number 27
======================================================
WARNING: possible circular locking dependency detected
5.3.0-rc7+ #0 Not tainted
------------------------------------------------------
kworker/1:5/2876 is trying to acquire lock:
000000006f0f0bc3 (minor_rwsem){++++}, at: usb_deregister_dev+0x95/0x230  
drivers/usb/core/file.c:239

but task is already holding lock:
00000000175691a3 (open_disc_mutex){+.+.}, at: tower_disconnect+0x45/0x300  
drivers/usb/misc/legousbtower.c:945

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (open_disc_mutex){+.+.}:
        __mutex_lock_common kernel/locking/mutex.c:930 [inline]
        __mutex_lock+0x158/0x1360 kernel/locking/mutex.c:1077
        tower_open+0xce/0x9b0 drivers/usb/misc/legousbtower.c:335
        usb_open+0x1df/0x270 drivers/usb/core/file.c:48
        chrdev_open+0x219/0x5c0 fs/char_dev.c:414
        do_dentry_open+0x494/0x1120 fs/open.c:797
        do_last fs/namei.c:3416 [inline]
        path_openat+0x1430/0x3f50 fs/namei.c:3533
        do_filp_open+0x1a1/0x280 fs/namei.c:3563
        do_sys_open+0x3c0/0x580 fs/open.c:1089
        do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
        entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (minor_rwsem){++++}:
        check_prev_add kernel/locking/lockdep.c:2405 [inline]
        check_prevs_add kernel/locking/lockdep.c:2507 [inline]
        validate_chain kernel/locking/lockdep.c:2897 [inline]
        __lock_acquire+0x1f7c/0x3b50 kernel/locking/lockdep.c:3880
        lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4412
        down_write+0x92/0x150 kernel/locking/rwsem.c:1500
        usb_deregister_dev+0x95/0x230 drivers/usb/core/file.c:239
        tower_disconnect+0xa8/0x300 drivers/usb/misc/legousbtower.c:951
        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+0x2dc/0x4a0 drivers/base/bus.c:556
        device_del+0x420/0xb10 drivers/base/core.c:2339
        usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
        usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2199
        hub_port_connect drivers/usb/core/hub.c:4949 [inline]
        hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
        port_event drivers/usb/core/hub.c:5359 [inline]
        hub_event+0x1454/0x3640 drivers/usb/core/hub.c:5441
        process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
        worker_thread+0x96/0xe20 kernel/workqueue.c:2415
        kthread+0x318/0x420 kernel/kthread.c:255
        ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(open_disc_mutex);
                                lock(minor_rwsem);
                                lock(open_disc_mutex);
   lock(minor_rwsem);

  *** DEADLOCK ***

6 locks held by kworker/1:5/2876:
  #0: 00000000ecb9dcf5 ((wq_completion)usb_hub_wq){+.+.}, at:  
__write_once_size include/linux/compiler.h:226 [inline]
  #0: 00000000ecb9dcf5 ((wq_completion)usb_hub_wq){+.+.}, at:  
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
  #0: 00000000ecb9dcf5 ((wq_completion)usb_hub_wq){+.+.}, at: atomic64_set  
include/asm-generic/atomic-instrumented.h:855 [inline]
  #0: 00000000ecb9dcf5 ((wq_completion)usb_hub_wq){+.+.}, at:  
atomic_long_set include/asm-generic/atomic-long.h:40 [inline]
  #0: 00000000ecb9dcf5 ((wq_completion)usb_hub_wq){+.+.}, at: set_work_data  
kernel/workqueue.c:620 [inline]
  #0: 00000000ecb9dcf5 ((wq_completion)usb_hub_wq){+.+.}, at:  
set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline]
  #0: 00000000ecb9dcf5 ((wq_completion)usb_hub_wq){+.+.}, at:  
process_one_work+0x827/0x1530 kernel/workqueue.c:2240
  #1: 0000000009747c0c ((work_completion)(&hub->events)){+.+.}, at:  
process_one_work+0x85b/0x1530 kernel/workqueue.c:2244
  #2: 000000004bd4f175 (&dev->mutex){....}, at: device_lock  
include/linux/device.h:1223 [inline]
  #2: 000000004bd4f175 (&dev->mutex){....}, at: hub_event+0x17c/0x3640  
drivers/usb/core/hub.c:5387
  #3: 00000000668c8b60 (&dev->mutex){....}, at: device_lock  
include/linux/device.h:1223 [inline]
  #3: 00000000668c8b60 (&dev->mutex){....}, at: usb_disconnect+0x91/0x8d0  
drivers/usb/core/hub.c:2190
  #4: 00000000787026a9 (&dev->mutex){....}, at:  
device_release_driver_internal+0x23/0x500 drivers/base/dd.c:1162
  #5: 00000000175691a3 (open_disc_mutex){+.+.}, at:  
tower_disconnect+0x45/0x300 drivers/usb/misc/legousbtower.c:945

stack backtrace:
CPU: 1 PID: 2876 Comm: kworker/1:5 Not tainted 5.3.0-rc7+ #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+0xca/0x13e lib/dump_stack.c:113
  check_noncircular+0x345/0x3e0 kernel/locking/lockdep.c:1741
  check_prev_add kernel/locking/lockdep.c:2405 [inline]
  check_prevs_add kernel/locking/lockdep.c:2507 [inline]
  validate_chain kernel/locking/lockdep.c:2897 [inline]
  __lock_acquire+0x1f7c/0x3b50 kernel/locking/lockdep.c:3880
  lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4412
  down_write+0x92/0x150 kernel/locking/rwsem.c:1500
  usb_deregister_dev+0x95/0x230 drivers/usb/core/file.c:239
  tower_disconnect+0xa8/0x300 drivers/usb/misc/legousbtower.c:951
  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+0x2dc/0x4a0 drivers/base/bus.c:556
  device_del+0x420/0xb10 drivers/base/core.c:2339
  usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
  usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2199
  hub_port_connect drivers/usb/core/hub.c:4949 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
  port_event drivers/usb/core/hub.c:5359 [inline]
  hub_event+0x1454/0x3640 drivers/usb/core/hub.c:5441
  process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
  worker_thread+0x96/0xe20 kernel/workqueue.c:2415
  kthread+0x318/0x420 kernel/kthread.c:255
  ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
legousbtower 5-1:0.219: LEGO USB Tower #-160 now disconnected
usb 5-1: new high-speed USB device number 28 using dummy_hcd
usb 5-1: device descriptor read/64, error 18
usb 5-1: device descriptor read/64, error 18
usb 5-1: new high-speed USB device number 29 using dummy_hcd
usb 5-1: device descriptor read/64, error 18
usb 5-1: device descriptor read/64, error 18
usb usb5-port1: attempt power cycle
usb 5-1: new high-speed USB device number 30 using dummy_hcd
usb 4-1: new high-speed USB device number 9 using dummy_hcd
usb 4-1: Using ep0 maxpacket: 16
usb 4-1: config 0 interface 0 altsetting 0 endpoint 0x81 has an invalid  
bInterval 0, changing to 7
usb 4-1: config 0 interface 0 altsetting 0 has 1 endpoint descriptor,  
different from the interface descriptor's value: 9
usb 4-1: New USB device found, idVendor=0d8c, idProduct=0022, bcdDevice=  
0.00
usb 4-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 4-1: config 0 descriptor??
usbhid 4-1:0.0: can't add hid device: -71
usbhid: probe of 4-1:0.0 failed with error -71
usb 4-1: USB disconnect, device number 9


---
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:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: possible deadlock in usb_deregister_dev (2)
  2019-09-16 16:09 possible deadlock in usb_deregister_dev (2) syzbot
@ 2019-09-16 21:42 ` syzbot
  2019-09-17 12:24   ` Johan Hovold
       [not found] ` <20190917080119.3940-1-hdanton@sina.com>
  1 sibling, 1 reply; 5+ messages in thread
From: syzbot @ 2019-09-16 21:42 UTC (permalink / raw)
  To: andreyknvl, gregkh, linux-kernel, linux-usb, stern, syzkaller-bugs

syzbot has found a reproducer for the following crash on:

HEAD commit:    f0df5c1b usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git usb-fuzzer
console output: https://syzkaller.appspot.com/x/log.txt?x=175cdb95600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
dashboard link: https://syzkaller.appspot.com/bug?extid=f9549f5ee8a5416f0b95
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13961369600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=139c811d600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+f9549f5ee8a5416f0b95@syzkaller.appspotmail.com

usb 1-1: config 0 descriptor??
legousbtower 1-1:0.219: LEGO USB Tower firmware version is 129.136 build  
65535
legousbtower 1-1:0.219: LEGO USB Tower #-160 now attached to major 180  
minor 0
usb 1-1: USB disconnect, device number 2
======================================================
WARNING: possible circular locking dependency detected
5.3.0-rc7+ #0 Not tainted
------------------------------------------------------
kworker/0:1/12 is trying to acquire lock:
0000000098630ee4 (minor_rwsem){++++}, at: usb_deregister_dev+0x95/0x230  
drivers/usb/core/file.c:239

but task is already holding lock:
00000000d9ad5b6f (open_disc_mutex){+.+.}, at: tower_disconnect+0x45/0x300  
drivers/usb/misc/legousbtower.c:945

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (open_disc_mutex){+.+.}:
        __mutex_lock_common kernel/locking/mutex.c:930 [inline]
        __mutex_lock+0x158/0x1360 kernel/locking/mutex.c:1077
        tower_open+0xce/0x9b0 drivers/usb/misc/legousbtower.c:335
        usb_open+0x1df/0x270 drivers/usb/core/file.c:48
        chrdev_open+0x219/0x5c0 fs/char_dev.c:414
        do_dentry_open+0x494/0x1120 fs/open.c:797
        do_last fs/namei.c:3416 [inline]
        path_openat+0x1430/0x3f50 fs/namei.c:3533
        do_filp_open+0x1a1/0x280 fs/namei.c:3563
        do_sys_open+0x3c0/0x580 fs/open.c:1089
        do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
        entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (minor_rwsem){++++}:
        check_prev_add kernel/locking/lockdep.c:2405 [inline]
        check_prevs_add kernel/locking/lockdep.c:2507 [inline]
        validate_chain kernel/locking/lockdep.c:2897 [inline]
        __lock_acquire+0x1f7c/0x3b50 kernel/locking/lockdep.c:3880
        lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4412
        down_write+0x92/0x150 kernel/locking/rwsem.c:1500
        usb_deregister_dev+0x95/0x230 drivers/usb/core/file.c:239
        tower_disconnect+0xa8/0x300 drivers/usb/misc/legousbtower.c:951
        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+0x2dc/0x4a0 drivers/base/bus.c:556
        device_del+0x420/0xb10 drivers/base/core.c:2339
        usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
        usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2199
        hub_port_connect drivers/usb/core/hub.c:4949 [inline]
        hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
        port_event drivers/usb/core/hub.c:5359 [inline]
        hub_event+0x1454/0x3640 drivers/usb/core/hub.c:5441
        process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
        worker_thread+0x96/0xe20 kernel/workqueue.c:2415
        kthread+0x318/0x420 kernel/kthread.c:255
        ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(open_disc_mutex);
                                lock(minor_rwsem);
                                lock(open_disc_mutex);
   lock(minor_rwsem);

  *** DEADLOCK ***

6 locks held by kworker/0:1/12:
  #0: 00000000b8e7e1e7 ((wq_completion)usb_hub_wq){+.+.}, at:  
__write_once_size include/linux/compiler.h:226 [inline]
  #0: 00000000b8e7e1e7 ((wq_completion)usb_hub_wq){+.+.}, at:  
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
  #0: 00000000b8e7e1e7 ((wq_completion)usb_hub_wq){+.+.}, at: atomic64_set  
include/asm-generic/atomic-instrumented.h:855 [inline]
  #0: 00000000b8e7e1e7 ((wq_completion)usb_hub_wq){+.+.}, at:  
atomic_long_set include/asm-generic/atomic-long.h:40 [inline]
  #0: 00000000b8e7e1e7 ((wq_completion)usb_hub_wq){+.+.}, at: set_work_data  
kernel/workqueue.c:620 [inline]
  #0: 00000000b8e7e1e7 ((wq_completion)usb_hub_wq){+.+.}, at:  
set_work_pool_and_clear_pending kernel/workqueue.c:647 [inline]
  #0: 00000000b8e7e1e7 ((wq_completion)usb_hub_wq){+.+.}, at:  
process_one_work+0x827/0x1530 kernel/workqueue.c:2240
  #1: 0000000054d9228f ((work_completion)(&hub->events)){+.+.}, at:  
process_one_work+0x85b/0x1530 kernel/workqueue.c:2244
  #2: 00000000f97c245e (&dev->mutex){....}, at: device_lock  
include/linux/device.h:1223 [inline]
  #2: 00000000f97c245e (&dev->mutex){....}, at: hub_event+0x17c/0x3640  
drivers/usb/core/hub.c:5387
  #3: 0000000035f038d2 (&dev->mutex){....}, at: device_lock  
include/linux/device.h:1223 [inline]
  #3: 0000000035f038d2 (&dev->mutex){....}, at: usb_disconnect+0x91/0x8d0  
drivers/usb/core/hub.c:2190
  #4: 00000000accb22e6 (&dev->mutex){....}, at:  
device_release_driver_internal+0x23/0x500 drivers/base/dd.c:1162
  #5: 00000000d9ad5b6f (open_disc_mutex){+.+.}, at:  
tower_disconnect+0x45/0x300 drivers/usb/misc/legousbtower.c:945

stack backtrace:
CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.3.0-rc7+ #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+0xca/0x13e lib/dump_stack.c:113
  check_noncircular+0x345/0x3e0 kernel/locking/lockdep.c:1741
  check_prev_add kernel/locking/lockdep.c:2405 [inline]
  check_prevs_add kernel/locking/lockdep.c:2507 [inline]
  validate_chain kernel/locking/lockdep.c:2897 [inline]
  __lock_acquire+0x1f7c/0x3b50 kernel/locking/lockdep.c:3880
  lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4412
  down_write+0x92/0x150 kernel/locking/rwsem.c:1500
  usb_deregister_dev+0x95/0x230 drivers/usb/core/file.c:239
  tower_disconnect+0xa8/0x300 drivers/usb/misc/legousbtower.c:951
  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+0x2dc/0x4a0 drivers/base/bus.c:556
  device_del+0x420/0xb10 drivers/base/core.c:2339
  usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
  usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2199
  hub_port_connect drivers/usb/core/hub.c:4949 [inline]
  hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
  port_event drivers/usb/core/hub.c:5359 [inline]
  hub_event+0x1454/0x3640 drivers/usb/core/hub.c:5441
  process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
  ? pwq_dec


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: possible deadlock in usb_deregister_dev (2)
       [not found] ` <20190917080119.3940-1-hdanton@sina.com>
@ 2019-09-17 11:58   ` Andrey Konovalov
  0 siblings, 0 replies; 5+ messages in thread
From: Andrey Konovalov @ 2019-09-17 11:58 UTC (permalink / raw)
  To: Hillf Danton
  Cc: syzbot, Greg Kroah-Hartman, LKML, USB list, Alan Stern, syzkaller-bugs

On Tue, Sep 17, 2019 at 10:01 AM Hillf Danton <hdanton@sina.com> wrote:
>
>
> On Mon, 16 Sep 2019 14:42:06 -0700
> >
> > syzbot has found a reproducer for the following crash on:
> >
> > HEAD commit:    f0df5c1b usb-fuzzer: main usb gadget fuzzer driver
> > git tree:       https://github.com/google/kasan.git usb-fuzzer
> > console output: https://syzkaller.appspot.com/x/log.txt?x=175cdb95600000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
> > dashboard link: https://syzkaller.appspot.com/bug?extid=f9549f5ee8a5416f0b95
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13961369600000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=139c811d600000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+f9549f5ee8a5416f0b95@syzkaller.appspotmail.com
> >
> > ======================================================
> > WARNING: possible circular locking dependency detected
> > 5.3.0-rc7+ #0 Not tainted
> > ------------------------------------------------------
> > kworker/0:1/12 is trying to acquire lock:
> > 0000000098630ee4 (minor_rwsem){++++}, at: usb_deregister_dev+0x95/0x230
> > drivers/usb/core/file.c:239
> >
> > but task is already holding lock:
> > 00000000d9ad5b6f (open_disc_mutex){+.+.}, at: tower_disconnect+0x45/0x300
> > drivers/usb/misc/legousbtower.c:945
> >
> > which lock already depends on the new lock.
> >
> >
> > the existing dependency chain (in reverse order) is:
> >
> > -> #1 (open_disc_mutex){+.+.}:
> >         __mutex_lock_common kernel/locking/mutex.c:930 [inline]
> >         __mutex_lock+0x158/0x1360 kernel/locking/mutex.c:1077
> >         tower_open+0xce/0x9b0 drivers/usb/misc/legousbtower.c:335
> >         usb_open+0x1df/0x270 drivers/usb/core/file.c:48
> >         chrdev_open+0x219/0x5c0 fs/char_dev.c:414
> >         do_dentry_open+0x494/0x1120 fs/open.c:797
> >         do_last fs/namei.c:3416 [inline]
> >         path_openat+0x1430/0x3f50 fs/namei.c:3533
> >         do_filp_open+0x1a1/0x280 fs/namei.c:3563
> >         do_sys_open+0x3c0/0x580 fs/open.c:1089
> >         do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
> >         entry_SYSCALL_64_after_hwframe+0x49/0xbe
> >
> > -> #0 (minor_rwsem){++++}:
> >         check_prev_add kernel/locking/lockdep.c:2405 [inline]
> >         check_prevs_add kernel/locking/lockdep.c:2507 [inline]
> >         validate_chain kernel/locking/lockdep.c:2897 [inline]
> >         __lock_acquire+0x1f7c/0x3b50 kernel/locking/lockdep.c:3880
> >         lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4412
> >         down_write+0x92/0x150 kernel/locking/rwsem.c:1500
> >         usb_deregister_dev+0x95/0x230 drivers/usb/core/file.c:239
> >         tower_disconnect+0xa8/0x300 drivers/usb/misc/legousbtower.c:951
> >         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+0x2dc/0x4a0 drivers/base/bus.c:556
> >         device_del+0x420/0xb10 drivers/base/core.c:2339
> >         usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
> >         usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2199
> >         hub_port_connect drivers/usb/core/hub.c:4949 [inline]
> >         hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
> >         port_event drivers/usb/core/hub.c:5359 [inline]
> >         hub_event+0x1454/0x3640 drivers/usb/core/hub.c:5441
> >         process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
> >         worker_thread+0x96/0xe20 kernel/workqueue.c:2415
> >         kthread+0x318/0x420 kernel/kthread.c:255
> >         ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> >
> > other info that might help us debug this:
> >
> >   Possible unsafe locking scenario:
> >
> >         CPU0                    CPU1
> >         ----                    ----
> >    lock(open_disc_mutex);
> >                                 lock(minor_rwsem);
> >                                 lock(open_disc_mutex);
> >    lock(minor_rwsem);
> >
> >   *** DEADLOCK ***
>
> Fix 78663ecc344b

Hi Hillf,

Thanks for looking at these bugs. This bug has a reproducer, so you
can ask syzbot to test the fix by issuing a syz test command as
described here:

https://github.com/google/syzkaller/blob/master/docs/syzbot.md#usb-bugs

Thanks!

>
> --- a/drivers/usb/misc/legousbtower.c
> +++ b/drivers/usb/misc/legousbtower.c
> @@ -941,17 +941,31 @@ static void tower_disconnect (struct usb
>         struct lego_usb_tower *dev;
>         int minor;
>
> -       dev = usb_get_intfdata (interface);
>         mutex_lock(&open_disc_mutex);
> +       dev = usb_get_intfdata (interface);
>         usb_set_intfdata (interface, NULL);
>
>         minor = dev->minor;
>
> -       /* give back our minor */
> -       usb_deregister_dev (interface, &tower_class);
> -
>         mutex_lock(&dev->lock);
>         mutex_unlock(&open_disc_mutex);
> +       /*
> +        * give back our minor out of open_disc_mutex to shun deadlock like
> +
> +               Possible unsafe locking scenario:
> +
> +               CPU0                    CPU1
> +               ----                    ----
> +               disconnect path         open path
> +
> +               lock(open_disc_mutex);
> +                                       lock(minor_rwsem);
> +                                       lock(open_disc_mutex);
> +               lock(minor_rwsem);
> +
> +        * and we can do this since intfdata is reset with lock held.
> +        */
> +       usb_deregister_dev (interface, &tower_class);
>
>         /* if the device is not opened, then we clean up right now */
>         if (!dev->open_count) {
>

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: possible deadlock in usb_deregister_dev (2)
  2019-09-16 21:42 ` syzbot
@ 2019-09-17 12:24   ` Johan Hovold
  2019-09-17 12:42     ` syzbot
  0 siblings, 1 reply; 5+ messages in thread
From: Johan Hovold @ 2019-09-17 12:24 UTC (permalink / raw)
  To: syzbot
  Cc: andreyknvl, gregkh, linux-kernel, linux-usb, stern,
	syzkaller-bugs, Oliver Neukum

On Mon, Sep 16, 2019 at 02:42:06PM -0700, syzbot wrote:
> syzbot has found a reproducer for the following crash on:
> 
> HEAD commit:    f0df5c1b usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=175cdb95600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
> dashboard link: https://syzkaller.appspot.com/bug?extid=f9549f5ee8a5416f0b95
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13961369600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=139c811d600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+f9549f5ee8a5416f0b95@syzkaller.appspotmail.com
> 
> usb 1-1: config 0 descriptor??
> legousbtower 1-1:0.219: LEGO USB Tower firmware version is 129.136 build  
> 65535
> legousbtower 1-1:0.219: LEGO USB Tower #-160 now attached to major 180  
> minor 0
> usb 1-1: USB disconnect, device number 2
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.3.0-rc7+ #0 Not tainted
> ------------------------------------------------------
> kworker/0:1/12 is trying to acquire lock:
> 0000000098630ee4 (minor_rwsem){++++}, at: usb_deregister_dev+0x95/0x230  
> drivers/usb/core/file.c:239
> 
> but task is already holding lock:
> 00000000d9ad5b6f (open_disc_mutex){+.+.}, at: tower_disconnect+0x45/0x300  
> drivers/usb/misc/legousbtower.c:945
> 
> which lock already depends on the new lock.
> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #1 (open_disc_mutex){+.+.}:
>         __mutex_lock_common kernel/locking/mutex.c:930 [inline]
>         __mutex_lock+0x158/0x1360 kernel/locking/mutex.c:1077
>         tower_open+0xce/0x9b0 drivers/usb/misc/legousbtower.c:335
>         usb_open+0x1df/0x270 drivers/usb/core/file.c:48
>         chrdev_open+0x219/0x5c0 fs/char_dev.c:414
>         do_dentry_open+0x494/0x1120 fs/open.c:797
>         do_last fs/namei.c:3416 [inline]
>         path_openat+0x1430/0x3f50 fs/namei.c:3533
>         do_filp_open+0x1a1/0x280 fs/namei.c:3563
>         do_sys_open+0x3c0/0x580 fs/open.c:1089
>         do_syscall_64+0xb7/0x580 arch/x86/entry/common.c:296
>         entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> -> #0 (minor_rwsem){++++}:
>         check_prev_add kernel/locking/lockdep.c:2405 [inline]
>         check_prevs_add kernel/locking/lockdep.c:2507 [inline]
>         validate_chain kernel/locking/lockdep.c:2897 [inline]
>         __lock_acquire+0x1f7c/0x3b50 kernel/locking/lockdep.c:3880
>         lock_acquire+0x127/0x320 kernel/locking/lockdep.c:4412
>         down_write+0x92/0x150 kernel/locking/rwsem.c:1500
>         usb_deregister_dev+0x95/0x230 drivers/usb/core/file.c:239
>         tower_disconnect+0xa8/0x300 drivers/usb/misc/legousbtower.c:951
>         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+0x2dc/0x4a0 drivers/base/bus.c:556
>         device_del+0x420/0xb10 drivers/base/core.c:2339
>         usb_disable_device+0x211/0x690 drivers/usb/core/message.c:1237
>         usb_disconnect+0x284/0x8d0 drivers/usb/core/hub.c:2199
>         hub_port_connect drivers/usb/core/hub.c:4949 [inline]
>         hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
>         port_event drivers/usb/core/hub.c:5359 [inline]
>         hub_event+0x1454/0x3640 drivers/usb/core/hub.c:5441
>         process_one_work+0x92b/0x1530 kernel/workqueue.c:2269
>         worker_thread+0x96/0xe20 kernel/workqueue.c:2415
>         kthread+0x318/0x420 kernel/kthread.c:255
>         ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
> 
> other info that might help us debug this:
> 
>   Possible unsafe locking scenario:
> 
>         CPU0                    CPU1
>         ----                    ----
>    lock(open_disc_mutex);
>                                 lock(minor_rwsem);
>                                 lock(open_disc_mutex);
>    lock(minor_rwsem);
> 
>   *** DEADLOCK ***

This should be fixed by the below patch. Looks like we may have a
similar issue in a few more drivers. Fixing them up next.

Johan

#syz test: https://github.com/google/kasan.git f0df5c1b


From c2c2800f2687be963acc222045c8fd89f3877642 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Tue, 17 Sep 2019 12:32:22 +0200
Subject: [PATCH] USB: legousbtower: fix deadlock on disconnect

Fix a potential deadlock if disconnect races with open.

Since commit d4ead16f50f9 ("USB: prevent char device open/deregister
race") core holds an rw-semaphore while open is called and when
releasing the minor number during deregistration. This can lead to an
ABBA deadlock if a driver takes a lock in open which it also holds
during deregistration.

This effectively reverts commit 78663ecc344b ("USB: disconnect open race
in legousbtower") which needlessly introduced this issue after a generic
fix for this race had been added to core by commit d4ead16f50f9 ("USB:
prevent char device open/deregister race").

Fixes: 78663ecc344b ("USB: disconnect open race in legousbtower")
Cc: stable <stable@vger.kernel.org>	# 2.6.24
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Oliver Neukum <oneukum@suse.com>
Reported-by: syzbot+f9549f5ee8a5416f0b95@syzkaller.appspotmail.com
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/misc/legousbtower.c | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 006cf13b2199..c125f03436a1 100644
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -179,7 +179,6 @@ static const struct usb_device_id tower_table[] = {
 };
 
 MODULE_DEVICE_TABLE (usb, tower_table);
-static DEFINE_MUTEX(open_disc_mutex);
 
 #define LEGO_USB_TOWER_MINOR_BASE	160
 
@@ -332,18 +331,14 @@ static int tower_open (struct inode *inode, struct file *file)
 		goto exit;
 	}
 
-	mutex_lock(&open_disc_mutex);
 	dev = usb_get_intfdata(interface);
-
 	if (!dev) {
-		mutex_unlock(&open_disc_mutex);
 		retval = -ENODEV;
 		goto exit;
 	}
 
 	/* lock this device */
 	if (mutex_lock_interruptible(&dev->lock)) {
-		mutex_unlock(&open_disc_mutex);
 	        retval = -ERESTARTSYS;
 		goto exit;
 	}
@@ -351,12 +346,10 @@ static int tower_open (struct inode *inode, struct file *file)
 
 	/* allow opening only once */
 	if (dev->open_count) {
-		mutex_unlock(&open_disc_mutex);
 		retval = -EBUSY;
 		goto unlock_exit;
 	}
 	dev->open_count = 1;
-	mutex_unlock(&open_disc_mutex);
 
 	/* reset the tower */
 	result = usb_control_msg (dev->udev,
@@ -423,10 +416,9 @@ static int tower_release (struct inode *inode, struct file *file)
 
 	if (dev == NULL) {
 		retval = -ENODEV;
-		goto exit_nolock;
+		goto exit;
 	}
 
-	mutex_lock(&open_disc_mutex);
 	if (mutex_lock_interruptible(&dev->lock)) {
 	        retval = -ERESTARTSYS;
 		goto exit;
@@ -456,10 +448,7 @@ static int tower_release (struct inode *inode, struct file *file)
 
 unlock_exit:
 	mutex_unlock(&dev->lock);
-
 exit:
-	mutex_unlock(&open_disc_mutex);
-exit_nolock:
 	return retval;
 }
 
@@ -910,7 +899,6 @@ static int tower_probe (struct usb_interface *interface, const struct usb_device
 	if (retval) {
 		/* something prevented us from registering this driver */
 		dev_err(idev, "Not able to get a minor for this device.\n");
-		usb_set_intfdata (interface, NULL);
 		goto error;
 	}
 	dev->minor = interface->minor;
@@ -942,16 +930,13 @@ static void tower_disconnect (struct usb_interface *interface)
 	int minor;
 
 	dev = usb_get_intfdata (interface);
-	mutex_lock(&open_disc_mutex);
-	usb_set_intfdata (interface, NULL);
 
 	minor = dev->minor;
 
-	/* give back our minor */
+	/* give back our minor and prevent further open() */
 	usb_deregister_dev (interface, &tower_class);
 
 	mutex_lock(&dev->lock);
-	mutex_unlock(&open_disc_mutex);
 
 	/* if the device is not opened, then we clean up right now */
 	if (!dev->open_count) {
-- 
2.23.0


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: possible deadlock in usb_deregister_dev (2)
  2019-09-17 12:24   ` Johan Hovold
@ 2019-09-17 12:42     ` syzbot
  0 siblings, 0 replies; 5+ messages in thread
From: syzbot @ 2019-09-17 12:42 UTC (permalink / raw)
  To: andreyknvl, gregkh, johan, linux-kernel, linux-usb, oneukum,
	stern, syzkaller-bugs

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger  
crash:

Reported-and-tested-by:  
syzbot+f9549f5ee8a5416f0b95@syzkaller.appspotmail.com

Tested on:

commit:         f0df5c1b usb-fuzzer: main usb gadget fuzzer driver
git tree:       https://github.com/google/kasan.git
kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
dashboard link: https://syzkaller.appspot.com/bug?extid=f9549f5ee8a5416f0b95
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16753b2d600000

Note: testing is done by a robot and is best-effort only.

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, back to index

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-09-16 16:09 possible deadlock in usb_deregister_dev (2) syzbot
2019-09-16 21:42 ` syzbot
2019-09-17 12:24   ` Johan Hovold
2019-09-17 12:42     ` syzbot
     [not found] ` <20190917080119.3940-1-hdanton@sina.com>
2019-09-17 11:58   ` Andrey Konovalov

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