Message-ID: <CAAeHK+ys+7Ng+15JC7kqbHOCckVBRWJat3OR2+HCWNZR8Z4ijA@mail.gmail.com>
Date:   Mon, 12 Aug 2019 14:10:26 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     syzbot <syzbot+ca52394faa436d8131df@...kaller.appspotmail.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: possible deadlock in iowarrior_open

On Thu, Aug 1, 2019 at 5:28 PM syzbot
<syzbot+ca52394faa436d8131df@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    7f7867ff 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=17ab6aec600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=792eb47789f57810
> dashboard link: https://syzkaller.appspot.com/bug?extid=ca52394faa436d8131df
> 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+ca52394faa436d8131df@...kaller.appspotmail.com
>
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.3.0-rc2+ #23 Not tainted
> ------------------------------------------------------
> syz-executor.0/10062 is trying to acquire lock:
> 00000000527cb8c7 (iowarrior_open_disc_lock){+.+.}, at:
> iowarrior_open+0x8a/0x2a0 drivers/usb/misc/iowarrior.c:600
>
> but task is already holding lock:
> 0000000061445bc7 (iowarrior_mutex){+.+.}, at: iowarrior_open+0x23/0x2a0
> drivers/usb/misc/iowarrior.c:589
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #2 (iowarrior_mutex){+.+.}:
>         __mutex_lock_common kernel/locking/mutex.c:930 [inline]
>         __mutex_lock+0x158/0x1360 kernel/locking/mutex.c:1077
>         iowarrior_open+0x23/0x2a0 drivers/usb/misc/iowarrior.c:589
>         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
>
> -> #1 (minor_rwsem#2){++++}:
>         down_write+0x92/0x150 kernel/locking/rwsem.c:1500
>         usb_deregister_dev drivers/usb/core/file.c:238 [inline]
>         usb_deregister_dev+0x61/0x270 drivers/usb/core/file.c:230
>         iowarrior_disconnect+0xa8/0x2c0 drivers/usb/misc/iowarrior.c:873
>         usb_unbind_interface+0x1bd/0x8a0 drivers/usb/core/driver.c:423
>         __device_release_driver drivers/base/dd.c:1120 [inline]
>         device_release_driver_internal+0x404/0x4c0 drivers/base/dd.c:1151
>         bus_remove_device+0x2dc/0x4a0 drivers/base/bus.c:556
>         device_del+0x420/0xb10 drivers/base/core.c:2288
>         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 (iowarrior_open_disc_lock){+.+.}:
>         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
>         iowarrior_open+0x8a/0x2a0 drivers/usb/misc/iowarrior.c:600
>         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:
>
> Chain exists of:
>    iowarrior_open_disc_lock --> minor_rwsem#2 --> iowarrior_mutex
>
>   Possible unsafe locking scenario:
>
>         CPU0                    CPU1
>         ----                    ----
>    lock(iowarrior_mutex);
>                                 lock(minor_rwsem#2);
>                                 lock(iowarrior_mutex);
>    lock(iowarrior_open_disc_lock);
>
>   *** DEADLOCK ***
>
> 2 locks held by syz-executor.0/10062:
>   #0: 000000000fd8903d (minor_rwsem#2){++++}, at: usb_open+0x23/0x270
> drivers/usb/core/file.c:39
>   #1: 0000000061445bc7 (iowarrior_mutex){+.+.}, at:
> iowarrior_open+0x23/0x2a0 drivers/usb/misc/iowarrior.c:589
>
> stack backtrace:
> CPU: 0 PID: 10062 Comm: syz-executor.0 Not tainted 5.3.0-rc2+ #23
> 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
>   iowarrior_open+0x8a/0x2a0 drivers/usb/misc/iowarrior.c:600
>   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: 0033:0x413711
> 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:00007fbd98b927a0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
> RAX: ffffffffffffffda RBX: 6666666666666667 RCX: 0000000000413711
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007fbd98b92850
> RBP: 000000000075bf20 R08: 000000000000000f R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000293 R12: 00007fbd98b936d4
> R13: 00000000004c8bee R14: 00000000004dfa68 R15: 00000000ffffffff

#syz dup: possible deadlock in usb_deregister_dev

>
>
> ---
> 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.

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