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SubjectRE: [PATCH] media: staging/intel-ipu3: Implement lock for stream on/off operations
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Hi Sakari,

> -----Original Message-----
> From: Sakari Ailus [mailto:sakari.ailus@linux.intel.com]
> Sent: Wednesday, January 30, 2019 12:59 AM
> To: Mani, Rajmohan <rajmohan.mani@intel.com>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>; Greg Kroah-Hartman
> <gregkh@linuxfoundation.org>; linux-media@vger.kernel.org;
> devel@driverdev.osuosl.org; linux-kernel@vger.kernel.org; Laurent Pinchart
> <laurent.pinchart@ideasonboard.com>; Jacopo Mondi <jacopo@jmondi.org>;
> Qiu, Tian Shu <tian.shu.qiu@intel.com>; Cao, Bingbu
> <bingbu.cao@intel.com>; Zhi@paasikivi.fi.intel.com; Zhi, Yong
> <yong.zhi@intel.com>; hverkuil@xs4all.nl; tfiga@chromium.org
> 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@ideasonboard.com>
> > Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >
> > Signed-off-by: Rajmohan Mani <rajmohan.mani@intel.com>
> > ---
> > 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@linux.intel.com

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