Re: [PATCH v5 3/3] media: vimc: use-after-free fix - release vimc in the v4l_device release

[Dafna Hirschfeld <dafna.hirschfeld@collabora.com>]

Hi

On 22.01.20 17:39, Helen Koike wrote:
> Hi Dafna,
> 
> Thanks for the patch.
> 
> On 1/22/20 2:01 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. This is an optional callback since
>> subdevices don't need to implement it because they are already
>> unregistered in v4l2_device_unregister.
>>
>> .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.
>>
>> 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@collabora.com>
>> ---
>>   drivers/media/platform/vimc/vimc-capture.c | 12 ++---
>>   drivers/media/platform/vimc/vimc-common.c  |  2 -
>>   drivers/media/platform/vimc/vimc-common.h  | 25 ++++-----
>>   drivers/media/platform/vimc/vimc-core.c    | 61 +++++++++++++++-------
>>   drivers/media/platform/vimc/vimc-debayer.c | 19 ++-----
>>   drivers/media/platform/vimc/vimc-scaler.c  | 19 ++-----
>>   drivers/media/platform/vimc/vimc-sensor.c  | 18 ++-----
>>   7 files changed, 71 insertions(+), 85 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..616d5a6b0754 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
>>    */
> 
> Did you test the suggestion I gave in last patch?
> That instead of adding another callback here, to just remove the release functions of the subdevices,
> and add a check if the release cb isn't null just before calling it.
> With this, the release functions of the video nodes would be called first.
> 
I just tested you suggestion, here is the patch: https://gitlab.collabora.com/dafna/linux/commit/f59bc7c6643ce8f88aa33eb5e9f413a1aca99589
I get a kasan report:

[   37.736909] BUG: KASAN: use-after-free in v4l2_device_unregister+0xa7/0xf0 [videodev]
[   37.738110] Read of size 4 at addr ffff8881eb3f00bc by task bash/227
...

What happen is that the function v4l2_device_unregister loops over the subdevices and unregister them:

   /* Unregister subdevs */
         list_for_each_entry_safe(sd, next, &v4l2_dev->subdevs, list) {
                 v4l2_device_unregister_subdev(sd);
                 if (sd->flags & V4L2_SUBDEV_FL_IS_I2C)
                         v4l2_i2c_subdev_unregister(sd);
                 else if (sd->flags & V4L2_SUBDEV_FL_IS_SPI)
                         v4l2_spi_subdev_unregister(sd);
         }

when unregistering the first subdevice it also immediately calls the release callback because no one holds a fh for
/dev/v4l2-subdev* , but the release cb releases the memory where the 'sd' in the above loop resides, then when
referencing it in sd->flags it is after it is already freed.

Dafna

> I followed the discussion regarding fhs in media node and video, not that I'm against your changes,
> but I would like to understand a bit better why the simple fix suggested isn't enough.
> 
> Thanks
> Helen
> 
>>   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 +147,23 @@ 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_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_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_release(struct vimc_ent_device *ved);
>>   
>>   /**
>>    * vimc_pix_map_by_index - get vimc_pix_map struct by its index
>> @@ -195,7 +198,6 @@ 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 +210,6 @@ 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..306f9c293628 100644
>> --- a/drivers/media/platform/vimc/vimc-core.c
>> +++ b/drivers/media/platform/vimc/vimc-core.c
>> @@ -48,48 +48,51 @@ static struct vimc_ent_config ent_config[] = {
>>   	{
>>   		.name = "Sensor A",
>>   		.add = vimc_sen_add,
>> -		.rm = vimc_sen_rm,
>> +		.release = vimc_sen_release,
>>   	},
>>   	{
>>   		.name = "Sensor B",
>>   		.add = vimc_sen_add,
>> -		.rm = vimc_sen_rm,
>> +		.release = vimc_sen_release,
>>   	},
>>   	{
>>   		.name = "Debayer A",
>>   		.add = vimc_deb_add,
>> -		.rm = vimc_deb_rm,
>> +		.release = vimc_deb_release,
>>   	},
>>   	{
>>   		.name = "Debayer B",
>>   		.add = vimc_deb_add,
>> -		.rm = vimc_deb_rm,
>> +		.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,
>> +		.release = vimc_sen_release,
>>   	},
>>   	{
>>   		.name = "Scaler",
>>   		.add = vimc_sca_add,
>> -		.rm = vimc_sca_rm,
>> +		.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 +178,33 @@ 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->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 +218,6 @@ 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 +258,9 @@ 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 +270,9 @@ 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 +305,12 @@ 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 +321,8 @@ 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..baf6bf9f65b5 100644
>> --- a/drivers/media/platform/vimc/vimc-debayer.c
>> +++ b/drivers/media/platform/vimc/vimc-debayer.c
>> @@ -494,28 +494,16 @@ 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)
>> -{
>> -	struct vimc_deb_device *vdeb;
>> -
>> -	vdeb = container_of(ved, struct vimc_deb_device, ved);
>> -	v4l2_device_unregister_subdev(&vdeb->sd);
>> -}
>> -
>>   static const struct v4l2_ctrl_config vimc_deb_ctrl_class = {
>>   	.flags = V4L2_CTRL_FLAG_READ_ONLY | V4L2_CTRL_FLAG_WRITE_ONLY,
>>   	.id = VIMC_CID_VIMC_CLASS,
>> @@ -563,8 +551,7 @@ 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..7521439747c5 100644
>> --- a/drivers/media/platform/vimc/vimc-scaler.c
>> +++ b/drivers/media/platform/vimc/vimc-scaler.c
>> @@ -464,27 +464,15 @@ 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)
>> -{
>> -	struct vimc_sca_device *vsca;
>> -
>> -	vsca = container_of(ved, struct vimc_sca_device, ved);
>> -	v4l2_device_unregister_subdev(&vsca->sd);
>> -}
>> -
>>   struct vimc_ent_device *vimc_sca_add(struct vimc_device *vimc,
>>   				     const char *vcfg_name)
>>   {
>> @@ -504,8 +492,7 @@ 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..92daee58209e 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);
>> @@ -290,18 +290,6 @@ 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)
>> -{
>> -	struct vimc_sen_device *vsen;
>> -
>> -	vsen = container_of(ved, struct vimc_sen_device, ved);
>> -	v4l2_device_unregister_subdev(&vsen->sd);
>> -}
>> -
>>   /* Image Processing Controls */
>>   static const struct v4l2_ctrl_config vimc_sen_ctrl_class = {
>>   	.flags = V4L2_CTRL_FLAG_READ_ONLY | V4L2_CTRL_FLAG_WRITE_ONLY,
>> @@ -365,7 +353,7 @@ 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;
>>   
>>