From: Oliver Neukum <oneukum@suse.com>
To: Jonathan Bell <jonathan@raspberrypi.org>
Cc: Minas Harutyunyan <hminas@synopsys.com>, linux-usb@vger.kernel.org
Subject: Re: dwc2 / Raspberry Pi - hardware bug for small transfers results in memory corruption
Date: Thu, 15 Aug 2019 16:52:17 +0200 [thread overview]
Message-ID: <1565880737.5780.12.camel@suse.com> (raw)
In-Reply-To: <CAPHs_JLkWmgvWJPyBdugFPfgPMpyeQL1bQe3VLru4BTf9L+iag@mail.gmail.com>
Am Donnerstag, den 15.08.2019, 12:41 +0100 schrieb Jonathan Bell:
> On Thu, Aug 15, 2019 at 11:55 AM Oliver Neukum <oneukum@suse.com> wrote:
> >
> > Am Mittwoch, den 14.08.2019, 16:59 +0100 schrieb Jonathan Bell:
> > > As reported by one of our users here:
> > > https://github.com/raspberrypi/linux/issues/3148
> > >
> > > There is a bug when the dwc2 core receives USB data packets that are
> > > between 1 and 4 bytes in length - 4 bytes are always written to memory
> > > where the non-packet bytes are garbage.
> >
> > Hi,
> >
> > in which function does that happen? If your buffer cannot handle 4
> > bytes I cannot see how it copes with teh DMA rules.
> >
>
> In drivers/media/usb/uvc/uvc_ctrl.c:uvc_ctrl_populate_cache() and friends.
OK, I see.
> The UVC driver passes in offsets into a struct uvc_control as the
> "buffer" that usb_control_msg() fills.
Not quite that bad. It passes a pointer into the middle of a buffer
used at different offsets for the transfer. This is technically allowed
as long as you never touch the buffer while a transfer is ongoing.
That is an accident waiting to happen. Please make a patch using
a bounce buffer allocated with knalloc() in
drivers/media/usb/uvc/uvc_ctrl.c:uvc_ctrl_populate_cache() and friends.
Regards
Oliver
next prev parent reply other threads:[~2019-08-15 14:52 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-14 15:59 dwc2 / Raspberry Pi - hardware bug for small transfers results in memory corruption Jonathan Bell
2019-08-15 10:55 ` Oliver Neukum
2019-08-15 11:41 ` Jonathan Bell
2019-08-15 14:37 ` Alan Stern
2019-08-15 14:52 ` Oliver Neukum [this message]
2019-08-16 22:18 ` Jonathan Bell
2019-08-19 11:01 ` Oliver Neukum
2019-08-15 12:51 ` Lars Melin
2019-08-15 12:54 ` Jonathan Bell
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