Re: [PATCH v4 3/6] media: vimc: use-after-free fix - release vimc in the v4l_device release

[Dafna Hirschfeld <dafna.hirschfeld@xxxxxxxxxxxxx>]

Hi

On 14.01.20 02:22, Helen Koike wrote:
> Hi Dafna,
>
> Thanks for this patch.
>
> On 1/13/20 7:55 PM, Dafna Hirschfeld wrote:
> > A use-after-free bug occures when unbinding the device while it streams.
> > The 'struct vimc_ent_device' allocated for the 'Sensor A' is freed
> > when calling the sensor's 'rm' callback but the freed pointer is
> > later accessed in the function 'vimc_streamer_pipeline_terminate'.
> > To fix this bug, move the release callback of the vimc entities
> > and vimc_device to the release callback of v4l2_device.
> > The .rm callback of vimc_ent_config is replaced by two callbacks:
> > .unregister - this is called upon removing the device and
> > it unregisters the entity.
> > .release - this is called from the release callback of v4l2_device
> > and it frees the entity.
> > This ensures that the entities will be released when the last fh
> > of any of the devices is closed.
>
> I have mixed feelings about this patch, because another solution would
> be to make sure to stop all streams before releasing the subdevices,
> which could be done by calling 'rm' callback from the capture nodes first.

> Also I noticed that calling v4l2_device_unregister_subdev() from the subdevices
> is a bit useless, since they are already called from v4l2_device_unregister(), who
> already iterates through all subdevices.
Yes, this is true, I can remove those lines.
> So what I suggest is to remove all the 'rm' callbacks from subdevices, and leave
> only the 'rm' from the capture entities.
>
> Rename vimc_rm_subdevs() to vimc_rm_video_devices()
>
> And you can loop like this:
>
> -static void vimc_rm_subdevs(struct vimc_device *vimc)
> +static void vimc_rm_video_devices(struct vimc_device *vimc)
>   {
>          unsigned int i;
>
>          for (i = 0; i < vimc->pipe_cfg->num_ents; i++)
> -               if (vimc->ent_devs[i])
> +               if (vimc->ent_devs[i] && vimc->pipe_cfg->ents[i].rm)
>                          vimc->pipe_cfg->ents[i].rm(vimc, vimc->ent_devs[i]);
>   }
>
> I didn't test, but I think it should work.
> Your patch would be cleaner (since you would be removing a bunch of lines),
> and we also would be re-using all the release functions from the media framework,
> which is nice for testing the core.
>
> What do you think?

The problem with releasing the subdevices in the releasing callback of 
the subdevice struct (the release of v4l2_subdev_internal_ops)
is that the release cb is called when the last fh of the specific 
subdevice is closed. This is a problem since the subdevice might still 
be referenced from other places in the code (which is what happen now in 
vimc) so the way to solve it is to release everything in the release 
callback of v4l2_device. This was also suggested by Hans.
(See 
https://lore.kernel.org/linux-media/a713212b-c760-f0c5-da5e-965d4fd87789@xxxxxxxxx/ 
)

I actaully don't see the point of having the release field in
v4l2_subdev_internal_ops if no driver implements it and it is actually
probably a bug if a dirver does implement it.

Dafna





> Thanks
> Helen
>
> > The commands that cause the crash and the KASAN report:
> >
> > media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]'
> > media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]'
> > v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=1920,height=1440
> > v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81
> > v4l2-ctl --stream-mmap --stream-count=1000 -d /dev/video2 &
> > sleep 1
> > echo -n vimc.0 >/sys/bus/platform/drivers/vimc/unbind
> >
> > [  188.417934] BUG: KASAN: use-after-free in vimc_streamer_pipeline_terminate+0x75/0x140 [vimc]
> > [  188.420182] Read of size 8 at addr ffff8881e9c26008 by task bash/185
> > [  188.421800]
> > [  188.422223] CPU: 0 PID: 185 Comm: bash Not tainted 5.5.0-rc1+ #1
> > [  188.423681] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
> > [  188.425938] Call Trace:
> > [  188.426610]  dump_stack+0x75/0xa0
> > [  188.427519]  ? vimc_streamer_pipeline_terminate+0x75/0x140 [vimc]
> > [  188.429057]  print_address_description.constprop.6+0x16/0x220
> > [  188.430462]  ? vimc_streamer_pipeline_terminate+0x75/0x140 [vimc]
> > [  188.431979]  ? vimc_streamer_pipeline_terminate+0x75/0x140 [vimc]
> > [  188.433455]  __kasan_report.cold.9+0x1a/0x40
> > [  188.434518]  ? vimc_streamer_pipeline_terminate+0x75/0x140 [vimc]
> > [  188.436010]  kasan_report+0xe/0x20
> > [  188.436859]  vimc_streamer_pipeline_terminate+0x75/0x140 [vimc]
> > [  188.438339]  vimc_streamer_s_stream+0x8b/0x3c0 [vimc]
> > [  188.439576]  vimc_cap_stop_streaming+0x22/0x40 [vimc]
> > [  188.440863]  __vb2_queue_cancel+0x65/0x560 [videobuf2_common]
> > [  188.442391]  vb2_core_queue_release+0x19/0x50 [videobuf2_common]
> > [  188.443974]  vimc_cap_rm+0x10/0x20 [vimc]
> > [  188.444986]  vimc_rm_subdevs+0x9e/0xe0 [vimc]
> > [  188.446179]  vimc_remove+0x19/0x70 [vimc]
> > [  188.447301]  platform_drv_remove+0x2f/0x50
> > [  188.448468]  device_release_driver_internal+0x133/0x260
> > [  188.449814]  unbind_store+0x121/0x150
> > [  188.450726]  kernfs_fop_write+0x142/0x230
> > [  188.451724]  ? sysfs_kf_bin_read+0x100/0x100
> > [  188.452826]  vfs_write+0xdc/0x230
> > [  188.453760]  ksys_write+0xaf/0x140
> > [  188.454702]  ? __ia32_sys_read+0x40/0x40
> > [  188.455773]  ? __do_page_fault+0x473/0x620
> > [  188.456780]  do_syscall_64+0x5e/0x1a0
> > [  188.457711]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > [  188.459079] RIP: 0033:0x7f80f1f13504
> > [  188.459969] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b3 0f 1f 80 00 00 00 00 48 8d 05 f9 61 0d 00 8b 00 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 41 54 49 89 d4 55 48 89 f5 53
> > [  188.464445] RSP: 002b:00007ffd7e843b58 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > [  188.466276] RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00007f80f1f13504
> > [  188.467999] RDX: 0000000000000006 RSI: 000055ef2eb21b10 RDI: 0000000000000001
> > [  188.469708] RBP: 000055ef2eb21b10 R08: 00007f80f1fe68c0 R09: 00007f80f1e26740
> > [  188.471407] R10: 000055ef2eade010 R11: 0000000000000246 R12: 00007f80f1fe5760
> > [  188.473381] R13: 0000000000000006 R14: 00007f80f1fe0760 R15: 0000000000000006
> > [  188.475107]
> > [  188.475500] Allocated by task 473:
> > [  188.476351]  save_stack+0x19/0x80
> > [  188.477201]  __kasan_kmalloc.constprop.6+0xc1/0xd0
> > [  188.478507]  vimc_sen_add+0x36/0x309 [vimc]
> > [  188.479649]  vimc_probe+0x1e2/0x530 [vimc]
> > [  188.480776]  platform_drv_probe+0x46/0xa0
> > [  188.481829]  really_probe+0x16c/0x520
> > [  188.482732]  driver_probe_device+0x114/0x170
> > [  188.483783]  device_driver_attach+0x85/0x90
> > [  188.484800]  __driver_attach+0xa8/0x190
> > [  188.485734]  bus_for_each_dev+0xe4/0x140
> > [  188.486702]  bus_add_driver+0x223/0x2d0
> > [  188.487715]  driver_register+0xca/0x140
> > [  188.488767]  0xffffffffc037003d
> > [  188.489635]  do_one_initcall+0x86/0x28f
> > [  188.490702]  do_init_module+0xf8/0x340
> > [  188.491773]  load_module+0x3766/0x3a10
> > [  188.492811]  __do_sys_finit_module+0x11a/0x1b0
> > [  188.494059]  do_syscall_64+0x5e/0x1a0
> > [  188.495079]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > [  188.496481]
> > [  188.496893] Freed by task 185:
> > [  188.497670]  save_stack+0x19/0x80
> > [  188.498493]  __kasan_slab_free+0x125/0x170
> > [  188.499486]  kfree+0x8c/0x230
> > [  188.500254]  v4l2_subdev_release+0x64/0x70 [videodev]
> > [  188.501498]  v4l2_device_release_subdev_node+0x1c/0x30 [videodev]
> > [  188.502976]  device_release+0x3c/0xd0
> > [  188.503867]  kobject_put+0xf4/0x240
> > [  188.507802]  vimc_rm_subdevs+0x9e/0xe0 [vimc]
> > [  188.508846]  vimc_remove+0x19/0x70 [vimc]
> > [  188.509792]  platform_drv_remove+0x2f/0x50
> > [  188.510752]  device_release_driver_internal+0x133/0x260
> > [  188.512006]  unbind_store+0x121/0x150
> > [  188.512899]  kernfs_fop_write+0x142/0x230
> > [  188.513874]  vfs_write+0xdc/0x230
> > [  188.514698]  ksys_write+0xaf/0x140
> > [  188.515523]  do_syscall_64+0x5e/0x1a0
> > [  188.516543]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > [  188.517710]
> > [  188.518034] The buggy address belongs to the object at ffff8881e9c26000
> > [  188.518034]  which belongs to the cache kmalloc-4k of size 4096
> > [  188.520528] The buggy address is located 8 bytes inside of
> > [  188.520528]  4096-byte region [ffff8881e9c26000, ffff8881e9c27000)
> > [  188.523015] The buggy address belongs to the page:
> > [  188.524357] page:ffffea0007a70800 refcount:1 mapcount:0 mapping:ffff8881f6402140 index:0x0 compound_mapcount: 0
> > [  188.527058] raw: 0200000000010200 dead000000000100 dead000000000122 ffff8881f6402140
> > [  188.528983] raw: 0000000000000000 0000000000040004 00000001ffffffff 0000000000000000
> > [  188.530883] page dumped because: kasan: bad access detected
> > [  188.532336]
> > [  188.532720] Memory state around the buggy address:
> > [  188.533871]  ffff8881e9c25f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > [  188.535631]  ffff8881e9c25f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > [  188.537370] >ffff8881e9c26000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [  188.538996]                       ^
> > [  188.539812]  ffff8881e9c26080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > [  188.541549]  ffff8881e9c26100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >
> > Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@xxxxxxxxxxxxx>
> > ---
> >   drivers/media/platform/vimc/vimc-capture.c | 12 ++--
> >   drivers/media/platform/vimc/vimc-common.c  |  2 -
> >   drivers/media/platform/vimc/vimc-common.h  | 28 +++++----
> >   drivers/media/platform/vimc/vimc-core.c    | 68 ++++++++++++++++------
> >   drivers/media/platform/vimc/vimc-debayer.c | 17 ++----
> >   drivers/media/platform/vimc/vimc-scaler.c  | 17 ++----
> >   drivers/media/platform/vimc/vimc-sensor.c  | 16 ++---
> >   7 files changed, 90 insertions(+), 70 deletions(-)
> >
> > diff --git a/drivers/media/platform/vimc/vimc-capture.c b/drivers/media/platform/vimc/vimc-capture.c
> > index 9a78bb7826a8..c5a645f98c66 100644
> > --- a/drivers/media/platform/vimc/vimc-capture.c
> > +++ b/drivers/media/platform/vimc/vimc-capture.c
> > @@ -325,20 +325,20 @@ static const struct media_entity_operations vimc_cap_mops = {
> >   	.link_validate		= vimc_vdev_link_validate,
> >   };
> >   
> > -static void vimc_cap_release(struct video_device *vdev)
> > +void vimc_cap_release(struct vimc_ent_device *ved)
> >   {
> >   	struct vimc_cap_device *vcap =
> > -		container_of(vdev, struct vimc_cap_device, vdev);
> > +		container_of(ved, struct vimc_cap_device, ved);
> >   
> >   	media_entity_cleanup(vcap->ved.ent);
> >   	kfree(vcap);
> >   }
> >   
> > -void vimc_cap_rm(struct vimc_device *vimc, struct vimc_ent_device *ved)
> > +void vimc_cap_unregister(struct vimc_ent_device *ved)
> >   {
> > -	struct vimc_cap_device *vcap;
> > +	struct vimc_cap_device *vcap =
> > +		container_of(ved, struct vimc_cap_device, ved);
> >   
> > -	vcap = container_of(ved, struct vimc_cap_device, ved);
> >   	vb2_queue_release(&vcap->queue);
> >   	video_unregister_device(&vcap->vdev);
> >   }
> > @@ -449,7 +449,7 @@ struct vimc_ent_device *vimc_cap_add(struct vimc_device *vimc,
> >   	vdev = &vcap->vdev;
> >   	vdev->device_caps = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING;
> >   	vdev->entity.ops = &vimc_cap_mops;
> > -	vdev->release = vimc_cap_release;
> > +	vdev->release = video_device_release_empty;
> >   	vdev->fops = &vimc_cap_fops;
> >   	vdev->ioctl_ops = &vimc_cap_ioctl_ops;
> >   	vdev->lock = &vcap->lock;
> > diff --git a/drivers/media/platform/vimc/vimc-common.c b/drivers/media/platform/vimc/vimc-common.c
> > index 16ce9f3b7c75..c95c17c048f2 100644
> > --- a/drivers/media/platform/vimc/vimc-common.c
> > +++ b/drivers/media/platform/vimc/vimc-common.c
> > @@ -327,7 +327,6 @@ int vimc_ent_sd_register(struct vimc_ent_device *ved,
> >   			 u32 function,
> >   			 u16 num_pads,
> >   			 struct media_pad *pads,
> > -			 const struct v4l2_subdev_internal_ops *sd_int_ops,
> >   			 const struct v4l2_subdev_ops *sd_ops)
> >   {
> >   	int ret;
> > @@ -337,7 +336,6 @@ int vimc_ent_sd_register(struct vimc_ent_device *ved,
> >   
> >   	/* Initialize the subdev */
> >   	v4l2_subdev_init(sd, sd_ops);
> > -	sd->internal_ops = sd_int_ops;
> >   	sd->entity.function = function;
> >   	sd->entity.ops = &vimc_ent_sd_mops;
> >   	sd->owner = THIS_MODULE;
> > diff --git a/drivers/media/platform/vimc/vimc-common.h b/drivers/media/platform/vimc/vimc-common.h
> > index 1b6ef7196f3c..99beb2134d40 100644
> > --- a/drivers/media/platform/vimc/vimc-common.h
> > +++ b/drivers/media/platform/vimc/vimc-common.h
> > @@ -125,16 +125,18 @@ struct vimc_device {
> >    * @name			entity name
> >    * @ved				pointer to vimc_ent_device (a node in the
> >    *					topology)
> > - * @add				subdev add hook - initializes and registers
> > - *					subdev called from vimc-core
> > - * @rm				subdev rm hook - unregisters and frees
> > - *					subdev called from vimc-core
> > + * @add				initializes and registers
> > + *					vim entity - called from vimc-core
> > + * @unregister			unregisters vimc entity - called from vimc-core
> > + * @release			releases vimc entity - called from the v4l2_dev
> > + *					release callback
> >    */
> >   struct vimc_ent_config {
> >   	const char *name;
> >   	struct vimc_ent_device *(*add)(struct vimc_device *vimc,
> >   				       const char *vcfg_name);
> > -	void (*rm)(struct vimc_device *vimc, struct vimc_ent_device *ved);
> > +	void (*unregister)(struct vimc_ent_device *ved);
> > +	void (*release)(struct vimc_ent_device *ved);
> >   };
> >   
> >   /**
> > @@ -145,22 +147,26 @@ struct vimc_ent_config {
> >    */
> >   bool vimc_is_source(struct media_entity *ent);
> >   
> > -/* prototypes for vimc_ent_config add and rm hooks */
> > +/* prototypes for vimc_ent_config hooks */
> >   struct vimc_ent_device *vimc_cap_add(struct vimc_device *vimc,
> >   				     const char *vcfg_name);
> > -void vimc_cap_rm(struct vimc_device *vimc, struct vimc_ent_device *ved);
> > +void vimc_cap_unregister(struct vimc_ent_device *ved);
> > +void vimc_cap_release(struct vimc_ent_device *ved);
> >   
> >   struct vimc_ent_device *vimc_deb_add(struct vimc_device *vimc,
> >   				     const char *vcfg_name);
> > -void vimc_deb_rm(struct vimc_device *vimc, struct vimc_ent_device *ved);
> > +void vimc_deb_unregister(struct vimc_ent_device *ved);
> > +void vimc_deb_release(struct vimc_ent_device *ved);
> >   
> >   struct vimc_ent_device *vimc_sca_add(struct vimc_device *vimc,
> >   				     const char *vcfg_name);
> > -void vimc_sca_rm(struct vimc_device *vimc, struct vimc_ent_device *ved);
> > +void vimc_sca_unregister(struct vimc_ent_device *ved);
> > +void vimc_sca_release(struct vimc_ent_device *ved);
> >   
> >   struct vimc_ent_device *vimc_sen_add(struct vimc_device *vimc,
> >   				     const char *vcfg_name);
> > -void vimc_sen_rm(struct vimc_device *vimc, struct vimc_ent_device *ved);
> > +void vimc_sen_unregister(struct vimc_ent_device *ved);
> > +void vimc_sen_release(struct vimc_ent_device *ved);
> >   
> >   /**
> >    * vimc_pix_map_by_index - get vimc_pix_map struct by its index
> > @@ -195,7 +201,6 @@ const struct vimc_pix_map *vimc_pix_map_by_pixelformat(u32 pixelformat);
> >    * @num_pads:	number of pads to initialize
> >    * @pads:	the array of pads of the entity, the caller should set the
> >   		flags of the pads
> > - * @sd_int_ops:	pointer to &struct v4l2_subdev_internal_ops
> >    * @sd_ops:	pointer to &struct v4l2_subdev_ops.
> >    *
> >    * Helper function initialize and register the struct vimc_ent_device and struct
> > @@ -208,7 +213,6 @@ int vimc_ent_sd_register(struct vimc_ent_device *ved,
> >   			 u32 function,
> >   			 u16 num_pads,
> >   			 struct media_pad *pads,
> > -			 const struct v4l2_subdev_internal_ops *sd_int_ops,
> >   			 const struct v4l2_subdev_ops *sd_ops);
> >   
> >   /**
> > diff --git a/drivers/media/platform/vimc/vimc-core.c b/drivers/media/platform/vimc/vimc-core.c
> > index 1c55e0382f09..9d4e8bc89620 100644
> > --- a/drivers/media/platform/vimc/vimc-core.c
> > +++ b/drivers/media/platform/vimc/vimc-core.c
> > @@ -48,48 +48,57 @@ static struct vimc_ent_config ent_config[] = {
> >   	{
> >   		.name = "Sensor A",
> >   		.add = vimc_sen_add,
> > -		.rm = vimc_sen_rm,
> > +		.unregister = vimc_sen_unregister,
> > +		.release = vimc_sen_release,
> >   	},
> >   	{
> >   		.name = "Sensor B",
> >   		.add = vimc_sen_add,
> > -		.rm = vimc_sen_rm,
> > +		.unregister = vimc_sen_unregister,
> > +		.release = vimc_sen_release,
> >   	},
> >   	{
> >   		.name = "Debayer A",
> >   		.add = vimc_deb_add,
> > -		.rm = vimc_deb_rm,
> > +		.unregister = vimc_deb_unregister,
> > +		.release = vimc_deb_release,
> >   	},
> >   	{
> >   		.name = "Debayer B",
> >   		.add = vimc_deb_add,
> > -		.rm = vimc_deb_rm,
> > +		.unregister = vimc_deb_unregister,
> > +		.release = vimc_deb_release,
> >   	},
> >   	{
> >   		.name = "Raw Capture 0",
> >   		.add = vimc_cap_add,
> > -		.rm = vimc_cap_rm,
> > +		.unregister = vimc_cap_unregister,
> > +		.release = vimc_cap_release,
> >   	},
> >   	{
> >   		.name = "Raw Capture 1",
> >   		.add = vimc_cap_add,
> > -		.rm = vimc_cap_rm,
> > +		.unregister = vimc_cap_unregister,
> > +		.release = vimc_cap_release,
> >   	},
> >   	{
> >   		/* TODO: change this to vimc-input when it is implemented */
> >   		.name = "RGB/YUV Input",
> >   		.add = vimc_sen_add,
> > -		.rm = vimc_sen_rm,
> > +		.unregister = vimc_sen_unregister,
> > +		.release = vimc_sen_release,
> >   	},
> >   	{
> >   		.name = "Scaler",
> >   		.add = vimc_sca_add,
> > -		.rm = vimc_sca_rm,
> > +		.unregister = vimc_sca_unregister,
> > +		.release = vimc_sca_release,
> >   	},
> >   	{
> >   		.name = "RGB/YUV Capture",
> >   		.add = vimc_cap_add,
> > -		.rm = vimc_cap_rm,
> > +		.unregister = vimc_cap_unregister,
> > +		.release = vimc_cap_release,
> >   	},
> >   };
> >   
> > @@ -175,13 +184,34 @@ static int vimc_add_subdevs(struct vimc_device *vimc)
> >   	return 0;
> >   }
> >   
> > -static void vimc_rm_subdevs(struct vimc_device *vimc)
> > +static void vimc_release_subdevs(struct vimc_device *vimc)
> >   {
> >   	unsigned int i;
> >   
> >   	for (i = 0; i < vimc->pipe_cfg->num_ents; i++)
> >   		if (vimc->ent_devs[i])
> > -			vimc->pipe_cfg->ents[i].rm(vimc, vimc->ent_devs[i]);
> > +			vimc->pipe_cfg->ents[i].release(vimc->ent_devs[i]);
> > +}
> > +
> > +
> > +static void vimc_unregister_subdevs(struct vimc_device *vimc)
> > +{
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < vimc->pipe_cfg->num_ents; i++)
> > +		if (vimc->ent_devs[i])
> > +			vimc->pipe_cfg->ents[i].unregister(vimc->ent_devs[i]);
> > +}
> > +
> > +static void vimc_v4l2_dev_release(struct v4l2_device *v4l2_dev)
> > +{
> > +	struct vimc_device *vimc =
> > +		container_of(v4l2_dev, struct vimc_device, v4l2_dev);
> > +
> > +	vimc_release_subdevs(vimc);
> > +	media_device_cleanup(&vimc->mdev);
> > +	kfree(vimc->ent_devs);
> > +	kfree(vimc);
> >   }
> >   
> >   static int vimc_register_devices(struct vimc_device *vimc)
> > @@ -195,7 +225,6 @@ static int vimc_register_devices(struct vimc_device *vimc)
> >   			"v4l2 device register failed (err=%d)\n", ret);
> >   		return ret;
> >   	}
> > -
> >   	/* allocate ent_devs */
> >   	vimc->ent_devs = kcalloc(vimc->pipe_cfg->num_ents,
> >   				 sizeof(*vimc->ent_devs), GFP_KERNEL);
> > @@ -236,9 +265,9 @@ static int vimc_register_devices(struct vimc_device *vimc)
> >   
> >   err_mdev_unregister:
> >   	media_device_unregister(&vimc->mdev);
> > -	media_device_cleanup(&vimc->mdev);
> >   err_rm_subdevs:
> > -	vimc_rm_subdevs(vimc);
> > +	vimc_unregister_subdevs(vimc);
> > +	vimc_release_subdevs(vimc);
> >   	kfree(vimc->ent_devs);
> >   err_v4l2_unregister:
> >   	v4l2_device_unregister(&vimc->v4l2_dev);
> > @@ -248,11 +277,9 @@ static int vimc_register_devices(struct vimc_device *vimc)
> >   
> >   static void vimc_unregister(struct vimc_device *vimc)
> >   {
> > +	vimc_unregister_subdevs(vimc);
> >   	media_device_unregister(&vimc->mdev);
> > -	media_device_cleanup(&vimc->mdev);
> >   	v4l2_device_unregister(&vimc->v4l2_dev);
> > -	kfree(vimc->ent_devs);
> > -	kfree(vimc);
> >   }
> >   
> >   static int vimc_probe(struct platform_device *pdev)
> > @@ -285,7 +312,12 @@ static int vimc_probe(struct platform_device *pdev)
> >   		kfree(vimc);
> >   		return ret;
> >   	}
> > +	/*
> > +	 * the release cb is set only after successful registration.
> > +	 * if the registration fails, we release directly from probe
> > +	 */
> >   
> > +	vimc->v4l2_dev.release = vimc_v4l2_dev_release;
> >   	platform_set_drvdata(pdev, vimc);
> >   	return 0;
> >   }
> > @@ -296,8 +328,8 @@ static int vimc_remove(struct platform_device *pdev)
> >   
> >   	dev_dbg(&pdev->dev, "remove");
> >   
> > -	vimc_rm_subdevs(vimc);
> >   	vimc_unregister(vimc);
> > +	v4l2_device_put(&vimc->v4l2_dev);
> >   
> >   	return 0;
> >   }
> > diff --git a/drivers/media/platform/vimc/vimc-debayer.c b/drivers/media/platform/vimc/vimc-debayer.c
> > index 34b98b235880..3beec7f95b47 100644
> > --- a/drivers/media/platform/vimc/vimc-debayer.c
> > +++ b/drivers/media/platform/vimc/vimc-debayer.c
> > @@ -494,25 +494,21 @@ static const struct v4l2_ctrl_ops vimc_deb_ctrl_ops = {
> >   	.s_ctrl = vimc_deb_s_ctrl,
> >   };
> >   
> > -static void vimc_deb_release(struct v4l2_subdev *sd)
> > +void vimc_deb_release(struct vimc_ent_device *ved)
> >   {
> >   	struct vimc_deb_device *vdeb =
> > -				container_of(sd, struct vimc_deb_device, sd);
> > +		container_of(ved, struct vimc_deb_device, ved);
> >   
> >   	v4l2_ctrl_handler_free(&vdeb->hdl);
> >   	media_entity_cleanup(vdeb->ved.ent);
> >   	kfree(vdeb);
> >   }
> >   
> > -static const struct v4l2_subdev_internal_ops vimc_deb_int_ops = {
> > -	.release = vimc_deb_release,
> > -};
> > -
> > -void vimc_deb_rm(struct vimc_device *vimc, struct vimc_ent_device *ved)
> > +void vimc_deb_unregister(struct vimc_ent_device *ved)
> >   {
> > -	struct vimc_deb_device *vdeb;
> > +	struct vimc_deb_device *vdeb =
> > +		container_of(ved, struct vimc_deb_device, ved);
> >   
> > -	vdeb = container_of(ved, struct vimc_deb_device, ved);
> >   	v4l2_device_unregister_subdev(&vdeb->sd);
> >   }
> >   
> > @@ -563,8 +559,7 @@ struct vimc_ent_device *vimc_deb_add(struct vimc_device *vimc,
> >   	ret = vimc_ent_sd_register(&vdeb->ved, &vdeb->sd, v4l2_dev,
> >   				   vcfg_name,
> >   				   MEDIA_ENT_F_PROC_VIDEO_PIXEL_ENC_CONV, 2,
> > -				   vdeb->pads,
> > -				   &vimc_deb_int_ops, &vimc_deb_ops);
> > +				   vdeb->pads, &vimc_deb_ops);
> >   	if (ret)
> >   		goto err_free_hdl;
> >   
> > diff --git a/drivers/media/platform/vimc/vimc-scaler.c b/drivers/media/platform/vimc/vimc-scaler.c
> > index cb2dc24c3e59..de9bee504b59 100644
> > --- a/drivers/media/platform/vimc/vimc-scaler.c
> > +++ b/drivers/media/platform/vimc/vimc-scaler.c
> > @@ -464,24 +464,20 @@ static void *vimc_sca_process_frame(struct vimc_ent_device *ved,
> >   	return vsca->src_frame;
> >   };
> >   
> > -static void vimc_sca_release(struct v4l2_subdev *sd)
> > +void vimc_sca_release(struct vimc_ent_device *ved)
> >   {
> >   	struct vimc_sca_device *vsca =
> > -				container_of(sd, struct vimc_sca_device, sd);
> > +		container_of(ved, struct vimc_sca_device, ved);
> >   
> >   	media_entity_cleanup(vsca->ved.ent);
> >   	kfree(vsca);
> >   }
> >   
> > -static const struct v4l2_subdev_internal_ops vimc_sca_int_ops = {
> > -	.release = vimc_sca_release,
> > -};
> > -
> > -void vimc_sca_rm(struct vimc_device *vimc, struct vimc_ent_device *ved)
> > +void vimc_sca_unregister(struct vimc_ent_device *ved)
> >   {
> > -	struct vimc_sca_device *vsca;
> > +	struct vimc_sca_device *vsca =
> > +		container_of(ved, struct vimc_sca_device, ved);
> >   
> > -	vsca = container_of(ved, struct vimc_sca_device, ved);
> >   	v4l2_device_unregister_subdev(&vsca->sd);
> >   }
> >   
> > @@ -504,8 +500,7 @@ struct vimc_ent_device *vimc_sca_add(struct vimc_device *vimc,
> >   	ret = vimc_ent_sd_register(&vsca->ved, &vsca->sd, v4l2_dev,
> >   				   vcfg_name,
> >   				   MEDIA_ENT_F_PROC_VIDEO_SCALER, 2,
> > -				   vsca->pads,
> > -				   &vimc_sca_int_ops, &vimc_sca_ops);
> > +				   vsca->pads, &vimc_sca_ops);
> >   	if (ret) {
> >   		kfree(vsca);
> >   		return NULL;
> > diff --git a/drivers/media/platform/vimc/vimc-sensor.c b/drivers/media/platform/vimc/vimc-sensor.c
> > index 9788fe291193..14eeaf461e93 100644
> > --- a/drivers/media/platform/vimc/vimc-sensor.c
> > +++ b/drivers/media/platform/vimc/vimc-sensor.c
> > @@ -279,10 +279,10 @@ static const struct v4l2_ctrl_ops vimc_sen_ctrl_ops = {
> >   	.s_ctrl = vimc_sen_s_ctrl,
> >   };
> >   
> > -static void vimc_sen_release(struct v4l2_subdev *sd)
> > +void vimc_sen_release(struct vimc_ent_device *ved)
> >   {
> >   	struct vimc_sen_device *vsen =
> > -				container_of(sd, struct vimc_sen_device, sd);
> > +		container_of(ved, struct vimc_sen_device, ved);
> >   
> >   	v4l2_ctrl_handler_free(&vsen->hdl);
> >   	tpg_free(&vsen->tpg);
> > @@ -290,15 +290,11 @@ static void vimc_sen_release(struct v4l2_subdev *sd)
> >   	kfree(vsen);
> >   }
> >   
> > -static const struct v4l2_subdev_internal_ops vimc_sen_int_ops = {
> > -	.release = vimc_sen_release,
> > -};
> > -
> > -void vimc_sen_rm(struct vimc_device *vimc, struct vimc_ent_device *ved)
> > +void vimc_sen_unregister(struct vimc_ent_device *ved)
> >   {
> > -	struct vimc_sen_device *vsen;
> > +	struct vimc_sen_device *vsen =
> > +		container_of(ved, struct vimc_sen_device, ved);
> >   
> > -	vsen = container_of(ved, struct vimc_sen_device, ved);
> >   	v4l2_device_unregister_subdev(&vsen->sd);
> >   }
> >   
> > @@ -365,7 +361,7 @@ struct vimc_ent_device *vimc_sen_add(struct vimc_device *vimc,
> >   	ret = vimc_ent_sd_register(&vsen->ved, &vsen->sd, v4l2_dev,
> >   				   vcfg_name,
> >   				   MEDIA_ENT_F_CAM_SENSOR, 1, &vsen->pad,
> > -				   &vimc_sen_int_ops, &vimc_sen_ops);
> > +				   &vimc_sen_ops);
> >   	if (ret)
> >   		goto err_free_tpg;
> >