Hi Sakari, > Subject: Re: [PATCH] media: staging/intel-ipu3: Implement lock for stream > on/off operations > > Hi Raj, > > On Wed, Jan 30, 2019 at 05:17:15PM +0000, Mani, Rajmohan wrote: > > 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(). > > You could move acquiring the lock out of these functions. It would also seem > that there is device-wide streaming state etc. information to which the access > should also be serialised. Currently it's relying on the node-specific lock only > which does not help. > Ack. Let me look into this more. > Can you grab the lock right after dev_dbg() line in the function? > In order to reduce the amount of code that's run with the lock held, I placed the lock here. Do you see issues in calls to imgu_sd subdevs and media_pipeline_start(), without the lock being held? > The lock should be also acquired before testing imgu->streaming in > ipu3_vb2_buf_queue() to make sure it won't change in the meantime. > I thought about this and decided against this since the odds of multiple instances of applications, each of which using a single node simultaneously are less, in a typical camera use case. Please confirm if you see significant issues without the lock here, so we can add the lock here as well. > > > > > > /* 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); > > I'd also call ipu3_return_all_buffers() before releasing the lock: in principle the > user may have queued new buffers on the devices before the driver marks the > buffers as faulty. > > > > > > > > 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. */ > > > > > -- > Sakari Ailus > sakari.ailus@xxxxxxxxxxxxxxx _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
