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From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Thu, 2 May 2019 18:10:40 +0200
Message-ID: <CAAeHK+x40G6B9penzkSHNqTXSg9ZfxrfD0hsmtJgm-O95nzcjw@mail.gmail.com>
Subject: Re: WARNING: Detected a wedged cx25840 chip; the device will not work.
To:     Alan Stern <stern@rowland.harvard.edu>
Cc:     Mike Isely <isely@pobox.com>,
        syzbot <syzbot+170a86bf206dd2c6217e@syzkaller.appspotmail.com>,
        linux-media@vger.kernel.org,
        Kernel development list <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
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On Tue, Apr 30, 2019 at 9:34 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Tue, 30 Apr 2019, syzbot wrote:
>
> > Hello,
> >
> > syzbot has tested the proposed patch but the reproducer still triggered
> > crash:
> > WARNING in sysfs_remove_group
> >
> > pvrusb2: Attached sub-driver tuner
> > pvrusb2: ***WARNING*** pvrusb2 driver initialization failed due to the
> > failure of one or more sub-device kernel modules.
> > pvrusb2: You need to resolve the failing condition before this driver can
> > function.  There should be some earlier messages giving more information
> > about the problem.
> > ------------[ cut here ]------------
> > sysfs group 'power' not found for kobject '0-0044'
> > WARNING: CPU: 1 PID: 586 at fs/sysfs/group.c:254 sysfs_remove_group
> > fs/sysfs/group.c:254 [inline]
> > WARNING: CPU: 1 PID: 586 at fs/sysfs/group.c:254
> > sysfs_remove_group+0x15a/0x1b0 fs/sysfs/group.c:245
> > Kernel panic - not syncing: panic_on_warn set ...
> > CPU: 1 PID: 586 Comm: pvrusb2-context Not tainted 5.1.0-rc3-g43151d6-dirty
> > #1
> > 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+0xe8/0x16e lib/dump_stack.c:113
> >   panic+0x29d/0x5f2 kernel/panic.c:214
> >   __warn.cold+0x20/0x48 kernel/panic.c:571
> >   report_bug+0x262/0x2a0 lib/bug.c:186
> >   fixup_bug arch/x86/kernel/traps.c:179 [inline]
> >   fixup_bug arch/x86/kernel/traps.c:174 [inline]
> >   do_error_trap+0x130/0x1f0 arch/x86/kernel/traps.c:272
> >   do_invalid_op+0x37/0x40 arch/x86/kernel/traps.c:291
> >   invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
> > RIP: 0010:sysfs_remove_group fs/sysfs/group.c:254 [inline]
> > RIP: 0010:sysfs_remove_group+0x15a/0x1b0 fs/sysfs/group.c:245
> > Code: 48 89 d9 49 8b 14 24 48 b8 00 00 00 00 00 fc ff df 48 c1 e9 03 80 3c
> > 01 00 75 41 48 8b 33 48 c7 c7 a0 31 7a 8e e8 e6 c2 6e ff <0f> 0b eb 95 e8
> > 0d de d3 ff e9 d2 fe ff ff 48 89 df e8 00 de d3 ff
> > RSP: 0018:ffff88809ced7b70 EFLAGS: 00010286
> > RAX: 0000000000000000 RBX: ffffffff8f037e80 RCX: 0000000000000000
> > RDX: 0000000000000000 RSI: ffffffff815b2132 RDI: ffffed10139daf60
> > RBP: 0000000000000000 R08: ffff88809ce96200 R09: ffffed1015a23edb
> > R10: ffffed1015a23eda R11: ffff8880ad11f6d7 R12: ffff888218b8e630
> > R13: ffffffff8f038520 R14: 1ffff110139daf97 R15: ffff888218b8e628
> >   dpm_sysfs_remove+0xa2/0xc0 drivers/base/power/sysfs.c:737
> >   device_del+0x175/0xb90 drivers/base/core.c:2246
> > usb 4-1: new high-speed USB device number 3 using dummy_hcd
> >   device_unregister+0x27/0xd0 drivers/base/core.c:2301
> >   i2c_unregister_device drivers/i2c/i2c-core-base.c:814 [inline]
> >   __unregister_client drivers/i2c/i2c-core-base.c:1422 [inline]
> >   __unregister_client+0x7d/0x90 drivers/i2c/i2c-core-base.c:1418
> >   device_for_each_child+0x100/0x170 drivers/base/core.c:2401
> >   i2c_del_adapter drivers/i2c/i2c-core-base.c:1485 [inline]
> >   i2c_del_adapter+0x35b/0x640 drivers/i2c/i2c-core-base.c:1447
> >   pvr2_i2c_core_done+0x6e/0xbb
> > drivers/media/usb/pvrusb2/pvrusb2-i2c-core.c:662
> >   pvr2_hdw_destroy+0x17e/0x380 drivers/media/usb/pvrusb2/pvrusb2-hdw.c:2669
> >   pvr2_context_destroy+0x89/0x240
> > drivers/media/usb/pvrusb2/pvrusb2-context.c:79
> >   pvr2_context_check drivers/media/usb/pvrusb2/pvrusb2-context.c:146 [inline]
> >   pvr2_context_thread_func+0x65e/0x870
> > drivers/media/usb/pvrusb2/pvrusb2-context.c:167
> >   kthread+0x313/0x420 kernel/kthread.c:253
> >   ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
> > Kernel Offset: disabled
> > Rebooting in 86400 seconds..
> >
> >
> > Tested on:
> >
> > commit:         43151d6c 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=15433634a00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=274aad0cf966c3bc
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > patch:          https://syzkaller.appspot.com/x/patch.diff?x=13df3d24a00000
>
> It seems pretty clear that this problem is caused by the
> pvr2_context_thread trying to unregister the device before the main
> probe routine has finished registering it.
>
> I'm not familiar enough with this driver to want to fix the problem,
> however.  Someone else who knows the code better should work on it.

Yeah, it's a different bug than I intended to fix. I've sent patch for
the original issue (using "WARNING:") though.

>
> Alan Stern
>