linux-kernel - Re: [PATCH] misc/uss720: fix memory leak in uss720

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Message-ID: <CAD-N9QW+HA9F=CiWUJseLggNA6qJ=TLomE4rja1x-NGgEX_jpg@mail.gmail.com>
Date:   Fri, 14 May 2021 20:02:17 +0800
From:   慕冬亮 <mudongliangabcd@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     linux-usb@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        syzbot+636c58f40a86b4a879e7@...kaller.appspotmail.com
Subject: Re: [PATCH] misc/uss720: fix memory leak in uss720_probe

On Fri, May 14, 2021 at 7:52 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Fri, May 14, 2021 at 07:48:57PM +0800, 慕冬亮 wrote:
> > On Fri, May 14, 2021 at 7:14 PM Greg KH <gregkh@...uxfoundation.org> wrote:
> > >
> > > On Fri, May 14, 2021 at 07:03:17PM +0800, Dongliang Mu wrote:
> > > > uss720_probe forgets to decrease the refcount of usbdev in uss720_probe.
> > > > Fix this by decreasing the refcount of usbdev by usb_put_dev.
> > > >
> > > > BUG: memory leak
> > > > unreferenced object 0xffff888101113800 (size 2048):
> > > >   comm "kworker/0:1", pid 7, jiffies 4294956777 (age 28.870s)
> > > >   hex dump (first 32 bytes):
> > > >     ff ff ff ff 31 00 00 00 00 00 00 00 00 00 00 00  ....1...........
> > > >     00 00 00 00 00 00 00 00 00 00 00 00 03 00 00 00  ................
> > > >   backtrace:
> > > >     [<ffffffff82b8e822>] kmalloc include/linux/slab.h:554 [inline]
> > > >     [<ffffffff82b8e822>] kzalloc include/linux/slab.h:684 [inline]
> > > >     [<ffffffff82b8e822>] usb_alloc_dev+0x32/0x450 drivers/usb/core/usb.c:582
> > > >     [<ffffffff82b98441>] hub_port_connect drivers/usb/core/hub.c:5129 [inline]
> > > >     [<ffffffff82b98441>] hub_port_connect_change drivers/usb/core/hub.c:5363 [inline]
> > > >     [<ffffffff82b98441>] port_event drivers/usb/core/hub.c:5509 [inline]
> > > >     [<ffffffff82b98441>] hub_event+0x1171/0x20c0 drivers/usb/core/hub.c:5591
> > > >     [<ffffffff81259229>] process_one_work+0x2c9/0x600 kernel/workqueue.c:2275
> > > >     [<ffffffff81259b19>] worker_thread+0x59/0x5d0 kernel/workqueue.c:2421
> > > >     [<ffffffff81261228>] kthread+0x178/0x1b0 kernel/kthread.c:292
> > > >     [<ffffffff8100227f>] ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
> > > >
> > > > Reported-by: syzbot+636c58f40a86b4a879e7@...kaller.appspotmail.com
> > > > Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
> > > > ---
> > > >  drivers/usb/misc/uss720.c | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/drivers/usb/misc/uss720.c b/drivers/usb/misc/uss720.c
> > > > index b5d661644263..748139d26263 100644
> > > > --- a/drivers/usb/misc/uss720.c
> > > > +++ b/drivers/usb/misc/uss720.c
> > > > @@ -736,6 +736,7 @@ static int uss720_probe(struct usb_interface *intf,
> > > >       parport_announce_port(pp);
> > > >
> > > >       usb_set_intfdata(intf, pp);
> > > > +     usb_put_dev(usbdev);
> > > >       return 0;
> > > >
> > > >  probe_abort:
> > > > --
> > > > 2.25.1
> > > >
> > >
> > > Nice catch!
> >
> > Thanks.
> >
> > This should be a bug fix. From the document, "Fixes" tag is needed for
> > bug fixes.
>
> It would be good, yes, please resend with that added.

Sure. I will resend the patch.

>
> > How do I quickly get this bug-inducing commit? Any
> > suggestion here?
>
> look at the log for this one file to find where the offending change
> happend.  Try `git log -p drivers/usb/misc/uss720.c`

0f36163d3abefbda1b21a330b3fdf3c2dc076d94 [PATCH] usb: fix uss720
schedule with interrupts off

@@ -536,93 +682,91 @@ static struct parport_operations parport_uss720_ops =
static int uss720_probe(struct usb_interface *intf,
const struct usb_device_id *id)
{
- struct usb_device *usbdev = interface_to_usbdev(intf);
+ struct usb_device *usbdev = usb_get_dev(interface_to_usbdev(intf));

Then only the code only decreases the refcount at failure sites.

>
> thanks,
>
> greg k-h