From: Dan Carpenter <dan.carpenter@oracle.com>
To: Dongliang Mu <mudongliangabcd@gmail.com>
Cc: Hillf Danton <hdanton@sina.com>,
syzbot <syzbot+005037419ebdf14e1d87@syzkaller.appspotmail.com>,
Igor Matheus Andrade Torrente <igormtorrente@gmail.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-media@vger.kernel.org,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: [syzbot] KASAN: use-after-free Read in em28xx_close_extension
Date: Tue, 27 Jul 2021 18:33:23 +0300 [thread overview]
Message-ID: <20210727153323.GO1931@kadam> (raw)
In-Reply-To: <CAD-N9QUz_7pxAFda9QYjhJf6tGLYvHr7hF_qZ3DmtP=J_yqWAg@mail.gmail.com>
On Tue, Jul 27, 2021 at 11:13:13PM +0800, Dongliang Mu wrote:
> On Tue, Jul 27, 2021 at 10:15 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> >
> > On Tue, Jul 27, 2021 at 06:01:51PM +0800, Hillf Danton wrote:
> > > Along the probe path,
> > >
> > > em28xx_usb_probe
> > > dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> > > retval = em28xx_init_dev(dev, udev, intf, nr);
> > > em28xx_init_extension(dev);
> > > em28xx_ir_init(struct em28xx *dev)
> > > kref_get(&dev->ref);
> > >
> > > kref_init(&dev->ref);
> >
>
> Hi Dan,
>
> I have developed a patch [1] to fix this crash. Would you like to help
> me double-check if it correctly fixes the underlying bug?
>
> [1] [PATCH v2] [media] em28xx-input: fix refcount bug in
> em28xx_usb_disconnect https://lkml.org/lkml/2021/7/19/263
No one likes to review patches which aren't sent over email... :/
LKML.org doesn't give the message-id so I can't use b4 to download the
email.
That patch doesn't make any sense. We call kref_get() at the start of
the function so we need to call kref_put() at the end. The fact that
em28xx_ir_fini() calls kref_put() doesn't matter. We will only call
fini if the init() succeeds (hopefully). The em28xx_ir_init() error
handling is Ad Hoc Style but I don't see anything outright buggy.
I think Hillf's approach is correct.
regards,
dan carpenter
next prev parent reply other threads:[~2021-07-27 15:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-14 14:27 [syzbot] KASAN: use-after-free Read in em28xx_close_extension syzbot
[not found] ` <20210727100151.2051-1-hdanton@sina.com>
2021-07-27 14:14 ` Dan Carpenter
2021-07-27 15:13 ` Dongliang Mu
2021-07-27 15:33 ` Dan Carpenter [this message]
2021-07-28 13:39 ` Dan Carpenter
2021-10-01 8:55 ` syzbot
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