possible deadlock in tower_open

[syzbot]

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=13c8d14e600000
kernel config: https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
dashboard link: https://syzkaller.appspot.com/bug?extid=66935bec147fbf68d9f8
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+66935b...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.3.0-rc7+ #0 Not tainted
------------------------------------------------------
syz-executor.1/8155 is trying to acquire lock:
0000000086c1bdfc (open_disc_mutex){+.+.}, at: tower_open+0xce/0x9b0
drivers/usb/misc/legousbtower.c:335

but task is already holding lock:
000000000f520f73 (minor_rwsem){++++}, at: usb_open+0x23/0x270
drivers/usb/core/file.c:39

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (minor_rwsem){++++}:
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

-> #0 (open_disc_mutex){+.+.}:
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
__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

other info that might help us debug this:

Possible unsafe locking scenario:

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

*** DEADLOCK ***

1 lock held by syz-executor.1/8155:
#0: 000000000f520f73 (minor_rwsem){++++}, at: usb_open+0x23/0x270
drivers/usb/core/file.c:39

stack backtrace:
CPU: 0 PID: 8155 Comm: syz-executor.1 Not tainted 5.3.0-rc7+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
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
__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
RIP: 0033:0x4137d1
Code: 75 14 b8 02 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 19 00 00 c3 48
83 ec 08 e8 0a fa ff ff 48 89 04 24 b8 02 00 00 00 0f 05 <48> 8b 3c 24 48
89 c2 e8 53 fa ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007f56184c17a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 6666666666666667 RCX: 00000000004137d1
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007f56184c1850
RBP: 000000000075c070 R08: 000000000000000f R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 00007f56184c26d4
R13: 00000000004c8cab R14: 00000000004dfc78 R15: 00000000ffffffff


---
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[Johan Hovold]

On Mon, Sep 16, 2019 at 06:29:12AM -0700, syzbot wrote:
> 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=13c8d14e600000
> kernel config: https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
> dashboard link: https://syzkaller.appspot.com/bug?extid=66935bec147fbf68d9f8
> 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+66935b...@syzkaller.appspotmail.com
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.3.0-rc7+ #0 Not tainted
> ------------------------------------------------------
> syz-executor.1/8155 is trying to acquire lock:
> 0000000086c1bdfc (open_disc_mutex){+.+.}, at: tower_open+0xce/0x9b0
> drivers/usb/misc/legousbtower.c:335
>
> but task is already holding lock:
> 000000000f520f73 (minor_rwsem){++++}, at: usb_open+0x23/0x270
> drivers/usb/core/file.c:39
>
> which lock already depends on the new lock.

This looks like a duplicate of

https://lkml.kernel.org/r/000000000000d5...@google.com

Not sure if this is the right way to report this (quoting needed?):

#syz dup: possible deadlock in usb_deregister_dev (2)

Johan

[Andrey Konovalov]

Hi Johan,

You did it right, now the status is changed to "closed as dup":

https://syzkaller.appspot.com/bug?extid=66935bec147fbf68d9f8

Thanks!