Message-ID: <Pine.LNX.4.44L0.1909161236580.1489-100000@iolanthe.rowland.org>
Date:   Mon, 16 Sep 2019 12:40:32 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     syzbot <syzbot+19cf612d23f66bc19f22@...kaller.appspotmail.com>
cc:     andreyknvl@...gle.com, <gregkh@...uxfoundation.org>,
        <linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>,
        <miquel@...uba.ar>, <rio500-users@...ts.sourceforge.net>,
        <syzkaller-bugs@...glegroups.com>
Subject: Re: possible deadlock in open_rio (2)

On Mon, 16 Sep 2019, 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=11512cd1600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
> dashboard link: https://syzkaller.appspot.com/bug?extid=19cf612d23f66bc19f22
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16f92c6e600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10b9b85e600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+19cf612d23f66bc19f22@...kaller.appspotmail.com
> 
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.3.0-rc7+ #0 Not tainted
> ------------------------------------------------------
> syz-executor071/1724 is trying to acquire lock:
> 00000000f749c934 (rio500_mutex){+.+.}, at: open_rio+0x16/0xe0  
> drivers/usb/misc/rio500.c:65
> 
> but task is already holding lock:
> 000000009c24ba51 (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_register_dev drivers/usb/core/file.c:187 [inline]
>         usb_register_dev+0x131/0x670 drivers/usb/core/file.c:156
>         probe_rio.cold+0x53/0x237 drivers/usb/misc/rio500.c:474
>         usb_probe_interface+0x305/0x7a0 drivers/usb/core/driver.c:361
>         really_probe+0x281/0x6d0 drivers/base/dd.c:548
>         driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
>         __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
>         bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:454
>         __device_attach+0x217/0x360 drivers/base/dd.c:894
>         bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
>         device_add+0xae6/0x16f0 drivers/base/core.c:2165
>         usb_set_configuration+0xdf6/0x1670 drivers/usb/core/message.c:2023
>         generic_probe+0x9d/0xd5 drivers/usb/core/generic.c:210
>         usb_probe_device+0x99/0x100 drivers/usb/core/driver.c:266
>         really_probe+0x281/0x6d0 drivers/base/dd.c:548
>         driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
>         __device_attach_driver+0x1c2/0x220 drivers/base/dd.c:828
>         bus_for_each_drv+0x162/0x1e0 drivers/base/bus.c:454
>         __device_attach+0x217/0x360 drivers/base/dd.c:894
>         bus_probe_device+0x1e4/0x290 drivers/base/bus.c:514
>         device_add+0xae6/0x16f0 drivers/base/core.c:2165
>         usb_new_device.cold+0x6a4/0xe79 drivers/usb/core/hub.c:2536
>         hub_port_connect drivers/usb/core/hub.c:5098 [inline]
>         hub_port_connect_change drivers/usb/core/hub.c:5213 [inline]
>         port_event drivers/usb/core/hub.c:5359 [inline]
>         hub_event+0x1b5c/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 (rio500_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
>         open_rio+0x16/0xe0 drivers/usb/misc/rio500.c:65
>         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(rio500_mutex);
>                                 lock(minor_rwsem);
>    lock(rio500_mutex);
> 
>   *** DEADLOCK ***
> 
> 1 lock held by syz-executor071/1724:
>   #0: 000000009c24ba51 (minor_rwsem){++++}, at: usb_open+0x23/0x270  
> drivers/usb/core/file.c:39
> 
> stack backtrace:
> CPU: 0 PID: 1724 Comm: syz-executor071 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
>   open_rio+0x16/0xe0 drivers/usb/misc/rio500.c:65
>   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: 0033:0x401130
> Code: 01 f0 ff ff 0f 83 00 0b 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f  
> 44 00 00 83 3d 5d 0c 2d 00 00 75 14 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff  
> ff 0f 83 d4 0a 00 00 c3 48 83 ec 08 e8 3a 00 00 00
> RSP: 002b:00007ffca0216788 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000401130
> RDX: 0000000000000000 RSI: 0000000000000002 RDI: 00007ffca02167a0
> RBP: 00000000006cb018 R08: 0000000000000000 R09: 000000000000000f
> R10: 0000000000000064 R11: 0000000000000246 R12: 0000000000402090
> R13: 0000000000402120 R14: 0000000000000000 R15: 00
> 
> 
> ---
> 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@...glegroups.com.
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

This is undoubted the same as the previous bug report.  It should be 
fixed by commit 9472aff16ca0 in Greg KH's usb-next branch, but the 
fix is not yet in Linus's tree.

#syz dup: possible deadlock in open_rio

Alan Stern

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