linux-kernel - Re: KASAN: use-after-free Read in si470x_int_in

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Date:   Fri, 22 Nov 2019 10:35:14 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     syzbot <syzbot+9ca7a12fd736d93e0232@...kaller.appspotmail.com>
cc:     andreyknvl@...gle.com, <hverkuil@...all.nl>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <linux-usb@...r.kernel.org>, <mchehab@...nel.org>,
        <oneukum@...e.com>, <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-free Read in si470x_int_in_callback (2)

On Fri, 22 Nov 2019, syzbot wrote:

> Hello,
> 
> syzbot has tested the proposed patch but the reproducer still triggered  
> crash:
> INFO: rcu detected stall in dummy_timer
> 
> radio-si470x 1-1:0.0: non-zero urb status (-71)
> radio-si470x 4-1:0.0: non-zero urb status (-71)
> radio-si470x 3-1:0.0: non-zero urb status (-71)

Oliver:

The reason for this stall is because the driver goes into a tight
resubmit loop when the interrupt URB completes with an unrecognized
error status.  Instead, the driver should log an error message and
avoid resubmitting.  Error recovery can be done at a higher level.

In other words, change the

			goto resubmit; /* Maybe we can recover. */

line in the completion handler into a return.

Alan Stern