RE: [PATCH] media: staging/intel-ipu3: Implement lock for stream on/off operations

[Mani, Rajmohan]

Hi Sakari,

> -----Original Message-----
> From: Sakari Ailus [mailto:sakari.ailus@xxxxxxxxxxxxxxx]
> Sent: Wednesday, January 30, 2019 12:59 AM
> To: Mani, Rajmohan <rajmohan.mani@xxxxxxxxx>
> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>; Greg Kroah-Hartman
> <gregkh@xxxxxxxxxxxxxxxxxxx>; linux-media@xxxxxxxxxxxxxxx;
> devel@xxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Laurent Pinchart
> <laurent.pinchart@xxxxxxxxxxxxxxxx>; Jacopo Mondi <jacopo@xxxxxxxxxx>;
> Qiu, Tian Shu <tian.shu.qiu@xxxxxxxxx>; Cao, Bingbu
> <bingbu.cao@xxxxxxxxx>; Zhi@xxxxxxxxxxxxxxxxxxxxxx; Zhi, Yong
> <yong.zhi@xxxxxxxxx>; hverkuil@xxxxxxxxx; tfiga@xxxxxxxxxxxx
> Subject: Re: [PATCH] media: staging/intel-ipu3: Implement lock for stream
> on/off operations
> 
> Hi Rajmohan,
> 
> On Tue, Jan 29, 2019 at 02:27:36PM -0800, Rajmohan Mani wrote:
> > Currently concurrent stream off operations on ImgU nodes are not
> > synchronized, leading to use-after-free bugs (as reported by KASAN).
> >
> > [  250.090724] BUG: KASAN: use-after-free in
> > ipu3_dmamap_free+0xc5/0x116 [ipu3_imgu] [  250.090726] Read of size 8
> > at addr ffff888127b29bc0 by task yavta/18836 [  250.090731] Hardware
> > name: HP Soraka/Soraka, BIOS Google_Soraka.10431.17.0 03/22/2018 [
> 250.090732] Call Trace:
> > [  250.090735]  dump_stack+0x6a/0xb1
> > [  250.090739]  print_address_description+0x8e/0x279
> > [  250.090743]  ? ipu3_dmamap_free+0xc5/0x116 [ipu3_imgu] [
> > 250.090746]  kasan_report+0x260/0x28a [  250.090750]
> > ipu3_dmamap_free+0xc5/0x116 [ipu3_imgu] [  250.090754]
> > ipu3_css_pool_cleanup+0x24/0x37 [ipu3_imgu] [  250.090759]
> > ipu3_css_pipeline_cleanup+0x61/0xb9 [ipu3_imgu] [  250.090763]
> > ipu3_css_stop_streaming+0x1f2/0x321 [ipu3_imgu] [  250.090768]
> > imgu_s_stream+0x94/0x443 [ipu3_imgu] [  250.090772]  ?
> > ipu3_vb2_buf_queue+0x280/0x280 [ipu3_imgu] [  250.090775]  ?
> > vb2_dma_sg_unmap_dmabuf+0x16/0x6f [videobuf2_dma_sg] [  250.090778]
> ?
> > vb2_buffer_in_use+0x36/0x58 [videobuf2_common] [  250.090782]
> > ipu3_vb2_stop_streaming+0xf9/0x135 [ipu3_imgu]
> >
> > Implemented a lock to synchronize imgu stream on / off operations and
> > the modification of streaming flag (in struct imgu_device), to prevent
> > these issues.
> >
> > Reported-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > Suggested-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> >
> > Signed-off-by: Rajmohan Mani <rajmohan.mani@xxxxxxxxx>
> > ---
> >  drivers/staging/media/ipu3/ipu3-v4l2.c | 6 ++++++
> >  drivers/staging/media/ipu3/ipu3.c      | 3 +++
> >  drivers/staging/media/ipu3/ipu3.h      | 4 ++++
> >  3 files changed, 13 insertions(+)
> >
> > diff --git a/drivers/staging/media/ipu3/ipu3-v4l2.c
> > b/drivers/staging/media/ipu3/ipu3-v4l2.c
> > index c7936032beb9..cf7e917cd0c8 100644
> > --- a/drivers/staging/media/ipu3/ipu3-v4l2.c
> > +++ b/drivers/staging/media/ipu3/ipu3-v4l2.c
> > @@ -507,12 +507,15 @@ static int ipu3_vb2_start_streaming(struct
> vb2_queue *vq, unsigned int count)
> >  			goto fail_stop_pipeline;
> >  	}
> >
> > +	mutex_lock(&imgu->streaming_lock);
> > +
> 
> You appear to be using imgu_device.lock (while searching buffers to queue to
> the device) as well as imgu_video_device.lock (qbuf, dqbuf) to serialise access
> to imgu_video_device.buffers list.

Ack

> The two locks may be acquired at the same
> time but each by different processes. That needs to be addressed, but
> probably not in this patch.
> 

The node specific locks will be used by different processes and all of these processes
will be competing commonly (and successfully) for the imgu_device lock.
I will look into this more.

> I wonder if it'd be more simple to use imgu->lock here instead of adding a new
> one.
> 

Extending imgu->lock here, does not work in this case, as imgu_queue_buffers()
will be stuck acquiring imgu->lock, which was already acquired by imgu_s_stream()
through ipu3_vb2_start_streaming().

> >  	/* Start streaming of the whole pipeline now */
> >  	dev_dbg(dev, "IMGU streaming is ready to start");
> >  	r = imgu_s_stream(imgu, true);
> >  	if (!r)
> >  		imgu->streaming = true;
> >
> > +	mutex_unlock(&imgu->streaming_lock);
> >  	return 0;
> >
> >  fail_stop_pipeline:
> > @@ -543,6 +546,8 @@ static void ipu3_vb2_stop_streaming(struct
> vb2_queue *vq)
> >  		dev_err(&imgu->pci_dev->dev,
> >  			"failed to stop subdev streaming\n");
> >
> > +	mutex_lock(&imgu->streaming_lock);
> > +
> >  	/* Was this the first node with streaming disabled? */
> >  	if (imgu->streaming && ipu3_all_nodes_streaming(imgu, node)) {
> >  		/* Yes, really stop streaming now */ @@ -552,6 +557,7 @@
> static
> > void ipu3_vb2_stop_streaming(struct vb2_queue *vq)
> >  			imgu->streaming = false;
> >  	}
> >
> > +	mutex_unlock(&imgu->streaming_lock);
> >  	ipu3_return_all_buffers(imgu, node, VB2_BUF_STATE_ERROR);
> 
> >  	media_pipeline_stop(&node->vdev.entity);
> >  }
> > diff --git a/drivers/staging/media/ipu3/ipu3.c
> > b/drivers/staging/media/ipu3/ipu3.c
> > index d521b3afb8b1..2daee51cd845 100644
> > --- a/drivers/staging/media/ipu3/ipu3.c
> > +++ b/drivers/staging/media/ipu3/ipu3.c
> > @@ -635,6 +635,7 @@ static int imgu_pci_probe(struct pci_dev *pci_dev,
> >  		return r;
> >
> >  	mutex_init(&imgu->lock);
> > +	mutex_init(&imgu->streaming_lock);
> >  	atomic_set(&imgu->qbuf_barrier, 0);
> >  	init_waitqueue_head(&imgu->buf_drain_wq);
> >
> > @@ -699,6 +700,7 @@ static int imgu_pci_probe(struct pci_dev *pci_dev,
> >  	ipu3_css_set_powerdown(&pci_dev->dev, imgu->base);
> >  out_mutex_destroy:
> >  	mutex_destroy(&imgu->lock);
> > +	mutex_destroy(&imgu->streaming_lock);
> >
> >  	return r;
> >  }
> > @@ -716,6 +718,7 @@ static void imgu_pci_remove(struct pci_dev
> *pci_dev)
> >  	ipu3_dmamap_exit(imgu);
> >  	ipu3_mmu_exit(imgu->mmu);
> >  	mutex_destroy(&imgu->lock);
> > +	mutex_destroy(&imgu->streaming_lock);
> >  }
> >
> >  static int __maybe_unused imgu_suspend(struct device *dev) diff --git
> > a/drivers/staging/media/ipu3/ipu3.h
> > b/drivers/staging/media/ipu3/ipu3.h
> > index 04fc99f47ebb..f732315f0701 100644
> > --- a/drivers/staging/media/ipu3/ipu3.h
> > +++ b/drivers/staging/media/ipu3/ipu3.h
> > @@ -146,6 +146,10 @@ struct imgu_device {
> >  	 * vid_buf.list and css->queue
> >  	 */
> >  	struct mutex lock;
> > +
> > +	/* Lock to protect writes to streaming flag in this struct */
> > +	struct mutex streaming_lock;
> > +
> >  	/* Forbit streaming and buffer queuing during system suspend. */
> >  	atomic_t qbuf_barrier;
> >  	/* Indicate if system suspend take place while imgu is streaming. */
> 
> --
> Regards,
> 
> Sakari Ailus
> sakari.ailus@xxxxxxxxxxxxxxx