Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <000000000000c2ee6a059360376e@google.com> <Pine.LNX.4.44L0.1909251006040.14432-100000@netrider.rowland.org>
In-Reply-To: <Pine.LNX.4.44L0.1909251006040.14432-100000@netrider.rowland.org>
From:   Andrey Konovalov <andreyknvl@google.com>
Date:   Wed, 25 Sep 2019 17:34:38 +0200
Message-ID: <CAAeHK+zSYnRgUb_S9MwEp0rp5nk0YzpoVcYZOn_WooCW68EOmw@mail.gmail.com>
Subject: Re: WARNING in pvr2_i2c_core_done
To:     Alan Stern <stern@rowland.harvard.edu>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     syzbot <syzbot+e74a998ca8f1df9cc332@syzkaller.appspotmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        USB list <linux-usb@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Sep 25, 2019 at 4:10 PM Alan Stern <stern@rowland.harvard.edu> wrote:
>
> On Wed, 25 Sep 2019, syzbot wrote:
>
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    d9e63adc 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=16b5fcd5600000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=f4fa60e981ee8e6a
> > dashboard link: https://syzkaller.appspot.com/bug?extid=e74a998ca8f1df9cc332
> > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16ec07b1600000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13ff0871600000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+e74a998ca8f1df9cc332@syzkaller.appspotmail.com
> >
> > pvrusb2: Device being rendered inoperable
> > cx25840 0-0044: Unable to detect h/w, assuming cx23887
> > cx25840 0-0044: cx23887 A/V decoder found @ 0x88 (pvrusb2_a)
> > pvrusb2: Attached sub-driver cx25840
> > pvrusb2: ***WARNING*** pvrusb2 device hardware appears to be jammed and I
> > can't clear it.
> > pvrusb2: You might need to power cycle the pvrusb2 device in order to
> > recover.
> > ------------[ cut here ]------------
> > sysfs group 'power' not found for kobject 'i2c-0'
> > WARNING: CPU: 0 PID: 102 at fs/sysfs/group.c:278 sysfs_remove_group
> > fs/sysfs/group.c:278 [inline]
> > WARNING: CPU: 0 PID: 102 at fs/sysfs/group.c:278
> > sysfs_remove_group+0x155/0x1b0 fs/sysfs/group.c:269
>
> I have seen a lot of error messages like this one (i.e., "group 'power'
> not found for kobject"), in runs that involved fuzzing a completely
> different USB driver.  Initial testing failed to find a cause.
>
> This leads me to wonder whether the problem might lie somewhere else
> entirely.  A bug in some core kernel code?  Memory corruption?

AFAICS so far this has only been triggered from the usbvision driver
[1] and from the pvrusb2 driver (this report).

I wanted to loop in sysfs maintainers, but it seems that Greg and
Rafael are already cc'ed on this.

[1] https://syzkaller.appspot.com/bug?extid=7fa38a608b1075dfd634