diff mbox series

[v3,3/3] media: uvcvideo: Lock video streams and queues while unregistering

Message ID 20231121-guenter-mini-v3-3-d8a5eae2312b@chromium.org
State Superseded
Headers show
Series uvcvideo: Attempt N to land UVC race conditions fixes | expand

Commit Message

Ricardo Ribalda Nov. 21, 2023, 7:53 p.m. UTC 
From: Guenter Roeck <linux@roeck-us.net>

The call to uvc_disconnect() is not protected by any mutex.
This means it can and will be called while other accesses to the video
device are in progress. This can cause all kinds of race conditions,
including crashes such as the following.

usb 1-4: USB disconnect, device number 3
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 0 PID: 5633 Comm: V4L2CaptureThre Not tainted 4.19.113-08536-g5d29ca36db06 #1
Hardware name: GOOGLE Edgar, BIOS Google_Edgar.7287.167.156 03/25/2019
RIP: 0010:usb_ifnum_to_if+0x29/0x40
Code: <...>
RSP: 0018:ffffa46f42a47a80 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff904a396c9000
RDX: ffff904a39641320 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffa46f42a47a80 R08: 0000000000000002 R09: 0000000000000000
R10: 0000000000009975 R11: 0000000000000009 R12: 0000000000000000
R13: ffff904a396b3800 R14: ffff904a39e88000 R15: 0000000000000000
FS: 00007f396448e700(0000) GS:ffff904a3ba00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000016cb46000 CR4: 00000000001006f0
Call Trace:
 usb_hcd_alloc_bandwidth+0x1ee/0x30f
 usb_set_interface+0x1a3/0x2b7
 uvc_video_start_transfer+0x29b/0x4b8 [uvcvideo]
 uvc_video_start_streaming+0x91/0xdd [uvcvideo]
 uvc_start_streaming+0x28/0x5d [uvcvideo]
 vb2_start_streaming+0x61/0x143 [videobuf2_common]
 vb2_core_streamon+0xf7/0x10f [videobuf2_common]
 uvc_queue_streamon+0x2e/0x41 [uvcvideo]
 uvc_ioctl_streamon+0x42/0x5c [uvcvideo]
 __video_do_ioctl+0x33d/0x42a
 video_usercopy+0x34e/0x5ff
 ? video_ioctl2+0x16/0x16
 v4l2_ioctl+0x46/0x53
 do_vfs_ioctl+0x50a/0x76f
 ksys_ioctl+0x58/0x83
 __x64_sys_ioctl+0x1a/0x1e
 do_syscall_64+0x54/0xde

usb_set_interface() should not be called after the USB device has been
unregistered. However, in the above case the disconnect happened after
v4l2_ioctl() was called, but before the call to usb_ifnum_to_if().

Acquire various mutexes in uvc_unregister_video() to fix the majority
(maybe all) of the observed race conditions.

The uvc_device lock prevents races against suspend and resume calls
and the poll function.

The uvc_streaming lock prevents races against stream related functions;
for the most part, those are ioctls. This lock also requires other
functions using this lock to check if a video device is still registered
after acquiring it. For example, it was observed that the video device
was already unregistered by the time the stream lock was acquired in
uvc_ioctl_streamon().

The uvc_queue lock prevents races against queue functions, Most of
those are already protected by the uvc_streaming lock, but some
are called directly. This is done as added protection; an actual race
was not (yet) observed.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Comments

Ricardo Ribalda Nov. 22, 2023, 1:59 p.m. UTC | #1 
Hi Laurent

On Wed, 22 Nov 2023 at 14:14, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> CC'ing Dan Williams.
>
> On Wed, Nov 22, 2023 at 10:21:04AM +0000, Sakari Ailus wrote:
> > Hi Ricardo,
> >
> > On Tue, Nov 21, 2023 at 07:53:50PM +0000, Ricardo Ribalda wrote:
> > > From: Guenter Roeck <linux@roeck-us.net>
> > >
> > > The call to uvc_disconnect() is not protected by any mutex.
> > > This means it can and will be called while other accesses to the video
> > > device are in progress. This can cause all kinds of race conditions,
> > > including crashes such as the following.
> > >
> > > usb 1-4: USB disconnect, device number 3
> > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> > > PGD 0 P4D 0
> > > Oops: 0000 [#1] PREEMPT SMP PTI
> > > CPU: 0 PID: 5633 Comm: V4L2CaptureThre Not tainted 4.19.113-08536-g5d29ca36db06 #1
> > > Hardware name: GOOGLE Edgar, BIOS Google_Edgar.7287.167.156 03/25/2019
> > > RIP: 0010:usb_ifnum_to_if+0x29/0x40
> > > Code: <...>
> > > RSP: 0018:ffffa46f42a47a80 EFLAGS: 00010246
> > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff904a396c9000
> > > RDX: ffff904a39641320 RSI: 0000000000000001 RDI: 0000000000000000
> > > RBP: ffffa46f42a47a80 R08: 0000000000000002 R09: 0000000000000000
> > > R10: 0000000000009975 R11: 0000000000000009 R12: 0000000000000000
> > > R13: ffff904a396b3800 R14: ffff904a39e88000 R15: 0000000000000000
> > > FS: 00007f396448e700(0000) GS:ffff904a3ba00000(0000) knlGS:0000000000000000
> > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 0000000000000000 CR3: 000000016cb46000 CR4: 00000000001006f0
> > > Call Trace:
> > >  usb_hcd_alloc_bandwidth+0x1ee/0x30f
> > >  usb_set_interface+0x1a3/0x2b7
> > >  uvc_video_start_transfer+0x29b/0x4b8 [uvcvideo]
> > >  uvc_video_start_streaming+0x91/0xdd [uvcvideo]
> > >  uvc_start_streaming+0x28/0x5d [uvcvideo]
> > >  vb2_start_streaming+0x61/0x143 [videobuf2_common]
> > >  vb2_core_streamon+0xf7/0x10f [videobuf2_common]
> > >  uvc_queue_streamon+0x2e/0x41 [uvcvideo]
> > >  uvc_ioctl_streamon+0x42/0x5c [uvcvideo]
> > >  __video_do_ioctl+0x33d/0x42a
> > >  video_usercopy+0x34e/0x5ff
> > >  ? video_ioctl2+0x16/0x16
> > >  v4l2_ioctl+0x46/0x53
> > >  do_vfs_ioctl+0x50a/0x76f
> > >  ksys_ioctl+0x58/0x83
> > >  __x64_sys_ioctl+0x1a/0x1e
> > >  do_syscall_64+0x54/0xde
> > >
> > > usb_set_interface() should not be called after the USB device has been
> > > unregistered. However, in the above case the disconnect happened after
> > > v4l2_ioctl() was called, but before the call to usb_ifnum_to_if().
> > >
> > > Acquire various mutexes in uvc_unregister_video() to fix the majority
> > > (maybe all) of the observed race conditions.
> > >
> > > The uvc_device lock prevents races against suspend and resume calls
> > > and the poll function.
> > >
> > > The uvc_streaming lock prevents races against stream related functions;
> > > for the most part, those are ioctls. This lock also requires other
> > > functions using this lock to check if a video device is still registered
> > > after acquiring it. For example, it was observed that the video device
> > > was already unregistered by the time the stream lock was acquired in
> > > uvc_ioctl_streamon().
> > >
> > > The uvc_queue lock prevents races against queue functions, Most of
> > > those are already protected by the uvc_streaming lock, but some
> > > are called directly. This is done as added protection; an actual race
> > > was not (yet) observed.
> > >
> > > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > Cc: Alan Stern <stern@rowland.harvard.edu>
> > > Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> > > Reviewed-by: Tomasz Figa <tfiga@chromium.org>
> > > Reviewed-by: Sean Paul <seanpaul@chromium.org>
> > > Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > ---
> > >  drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
> > >  1 file changed, 9 insertions(+)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > > index 413c32867617..3408b865d346 100644
> > > --- a/drivers/media/usb/uvc/uvc_driver.c
> > > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > > @@ -1907,14 +1907,22 @@ static void uvc_unregister_video(struct uvc_device *dev)
> > >  {
> > >     struct uvc_streaming *stream;
> > >
> > > +   mutex_lock(&dev->lock);
> > > +
> > >     list_for_each_entry(stream, &dev->streams, list) {
> > >             if (!video_is_registered(&stream->vdev))
> > >                     continue;
> > >
> > > +           mutex_lock(&stream->mutex);
> > > +           mutex_lock(&stream->queue.mutex);
> > > +
> > >             video_unregister_device(&stream->vdev);
> > >             video_unregister_device(&stream->meta.vdev);
> > >
> > >             uvc_debugfs_cleanup_stream(stream);
> > > +
> > > +           mutex_unlock(&stream->queue.mutex);
> > > +           mutex_unlock(&stream->mutex);
> > >     }
> > >
> > >     uvc_status_unregister(dev);
> > > @@ -1925,6 +1933,7 @@ static void uvc_unregister_video(struct uvc_device *dev)
> > >     if (media_devnode_is_registered(dev->mdev.devnode))
> > >             media_device_unregister(&dev->mdev);
> > >  #endif
> > > +   mutex_unlock(&dev->lock);
> > >  }
> > >
> > >  int uvc_register_video_device(struct uvc_device *dev,
> > >
> >
> > Instead of acquiring all the possible locks, could you instead take the
> > same approach as you do with ISP? It should use refcount_t btw.
> > <URL:https://chromium.googlesource.com/chromiumos/third_party/kernel/+/refs/heads/kcam-6.1/drivers/isp/isp-device.c:
>
> The right approach, as I've said countless of times, is to fix this at
> the cdev and V4L2 level. Dan Williams has done some ground work on this
> a while ago ([1]), and before that I posted an RFC series that
> overlapped with Dan's work (with a more naive and less efficient
> implementation of refcounting, see [2]).
>
> [1] https://lore.kernel.org/all/161117153776.2853729.6944617921517514510.stgit@dwillia2-desk3.amr.corp.intel.com/
> [2] https://lore.kernel.org/linux-media/20171116003349.19235-2-laurent.pinchart+renesas@ideasonboard.com/

The UVC driver is violating the USB driver API [1] causing crashes and
probably security vulnerabilities. It has to be fixed.

If there was a different way TODAY to do this, I would very happily
implement it differently. But your patchset is 6 years old and Dan's 2
and they have not landed. How many kernel versions is ok to put our
users willingly at risk?

This patch simply serialises unregister_video? How can this patch
affect the viability of your patchset or Dan's patch? If this patch is
not needed in the future we can simply revert it.

When/If there is a better way to implement this, I would very happily
send a follow-up patch to use that framework.

[1] https://www.kernel.org/doc/html/latest/driver-api/usb/callbacks.html#the-disconnect-callback









>
> --
> Regards,
>
> Laurent Pinchart



--
Ricardo Ribalda
Laurent Pinchart Nov. 22, 2023, 2:04 p.m. UTC | #2 
Hi Ricardo,

On Wed, Nov 22, 2023 at 02:59:31PM +0100, Ricardo Ribalda wrote:
> On Wed, 22 Nov 2023 at 14:14, Laurent Pinchart wrote:
> > On Wed, Nov 22, 2023 at 10:21:04AM +0000, Sakari Ailus wrote:
> > > On Tue, Nov 21, 2023 at 07:53:50PM +0000, Ricardo Ribalda wrote:
> > > > From: Guenter Roeck <linux@roeck-us.net>
> > > >
> > > > The call to uvc_disconnect() is not protected by any mutex.
> > > > This means it can and will be called while other accesses to the video
> > > > device are in progress. This can cause all kinds of race conditions,
> > > > including crashes such as the following.
> > > >
> > > > usb 1-4: USB disconnect, device number 3
> > > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> > > > PGD 0 P4D 0
> > > > Oops: 0000 [#1] PREEMPT SMP PTI
> > > > CPU: 0 PID: 5633 Comm: V4L2CaptureThre Not tainted 4.19.113-08536-g5d29ca36db06 #1
> > > > Hardware name: GOOGLE Edgar, BIOS Google_Edgar.7287.167.156 03/25/2019
> > > > RIP: 0010:usb_ifnum_to_if+0x29/0x40
> > > > Code: <...>
> > > > RSP: 0018:ffffa46f42a47a80 EFLAGS: 00010246
> > > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff904a396c9000
> > > > RDX: ffff904a39641320 RSI: 0000000000000001 RDI: 0000000000000000
> > > > RBP: ffffa46f42a47a80 R08: 0000000000000002 R09: 0000000000000000
> > > > R10: 0000000000009975 R11: 0000000000000009 R12: 0000000000000000
> > > > R13: ffff904a396b3800 R14: ffff904a39e88000 R15: 0000000000000000
> > > > FS: 00007f396448e700(0000) GS:ffff904a3ba00000(0000) knlGS:0000000000000000
> > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > CR2: 0000000000000000 CR3: 000000016cb46000 CR4: 00000000001006f0
> > > > Call Trace:
> > > >  usb_hcd_alloc_bandwidth+0x1ee/0x30f
> > > >  usb_set_interface+0x1a3/0x2b7
> > > >  uvc_video_start_transfer+0x29b/0x4b8 [uvcvideo]
> > > >  uvc_video_start_streaming+0x91/0xdd [uvcvideo]
> > > >  uvc_start_streaming+0x28/0x5d [uvcvideo]
> > > >  vb2_start_streaming+0x61/0x143 [videobuf2_common]
> > > >  vb2_core_streamon+0xf7/0x10f [videobuf2_common]
> > > >  uvc_queue_streamon+0x2e/0x41 [uvcvideo]
> > > >  uvc_ioctl_streamon+0x42/0x5c [uvcvideo]
> > > >  __video_do_ioctl+0x33d/0x42a
> > > >  video_usercopy+0x34e/0x5ff
> > > >  ? video_ioctl2+0x16/0x16
> > > >  v4l2_ioctl+0x46/0x53
> > > >  do_vfs_ioctl+0x50a/0x76f
> > > >  ksys_ioctl+0x58/0x83
> > > >  __x64_sys_ioctl+0x1a/0x1e
> > > >  do_syscall_64+0x54/0xde
> > > >
> > > > usb_set_interface() should not be called after the USB device has been
> > > > unregistered. However, in the above case the disconnect happened after
> > > > v4l2_ioctl() was called, but before the call to usb_ifnum_to_if().
> > > >
> > > > Acquire various mutexes in uvc_unregister_video() to fix the majority
> > > > (maybe all) of the observed race conditions.
> > > >
> > > > The uvc_device lock prevents races against suspend and resume calls
> > > > and the poll function.
> > > >
> > > > The uvc_streaming lock prevents races against stream related functions;
> > > > for the most part, those are ioctls. This lock also requires other
> > > > functions using this lock to check if a video device is still registered
> > > > after acquiring it. For example, it was observed that the video device
> > > > was already unregistered by the time the stream lock was acquired in
> > > > uvc_ioctl_streamon().
> > > >
> > > > The uvc_queue lock prevents races against queue functions, Most of
> > > > those are already protected by the uvc_streaming lock, but some
> > > > are called directly. This is done as added protection; an actual race
> > > > was not (yet) observed.
> > > >
> > > > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > > Cc: Alan Stern <stern@rowland.harvard.edu>
> > > > Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> > > > Reviewed-by: Tomasz Figa <tfiga@chromium.org>
> > > > Reviewed-by: Sean Paul <seanpaul@chromium.org>
> > > > Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > > ---
> > > >  drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
> > > >  1 file changed, 9 insertions(+)
> > > >
> > > > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > > > index 413c32867617..3408b865d346 100644
> > > > --- a/drivers/media/usb/uvc/uvc_driver.c
> > > > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > > > @@ -1907,14 +1907,22 @@ static void uvc_unregister_video(struct uvc_device *dev)
> > > >  {
> > > >     struct uvc_streaming *stream;
> > > >
> > > > +   mutex_lock(&dev->lock);
> > > > +
> > > >     list_for_each_entry(stream, &dev->streams, list) {
> > > >             if (!video_is_registered(&stream->vdev))
> > > >                     continue;
> > > >
> > > > +           mutex_lock(&stream->mutex);
> > > > +           mutex_lock(&stream->queue.mutex);
> > > > +
> > > >             video_unregister_device(&stream->vdev);
> > > >             video_unregister_device(&stream->meta.vdev);
> > > >
> > > >             uvc_debugfs_cleanup_stream(stream);
> > > > +
> > > > +           mutex_unlock(&stream->queue.mutex);
> > > > +           mutex_unlock(&stream->mutex);
> > > >     }
> > > >
> > > >     uvc_status_unregister(dev);
> > > > @@ -1925,6 +1933,7 @@ static void uvc_unregister_video(struct uvc_device *dev)
> > > >     if (media_devnode_is_registered(dev->mdev.devnode))
> > > >             media_device_unregister(&dev->mdev);
> > > >  #endif
> > > > +   mutex_unlock(&dev->lock);
> > > >  }
> > > >
> > > >  int uvc_register_video_device(struct uvc_device *dev,
> > > >
> > >
> > > Instead of acquiring all the possible locks, could you instead take the
> > > same approach as you do with ISP? It should use refcount_t btw.
> > > <URL:https://chromium.googlesource.com/chromiumos/third_party/kernel/+/refs/heads/kcam-6.1/drivers/isp/isp-device.c:
> >
> > The right approach, as I've said countless of times, is to fix this at
> > the cdev and V4L2 level. Dan Williams has done some ground work on this
> > a while ago ([1]), and before that I posted an RFC series that
> > overlapped with Dan's work (with a more naive and less efficient
> > implementation of refcounting, see [2]).
> >
> > [1] https://lore.kernel.org/all/161117153776.2853729.6944617921517514510.stgit@dwillia2-desk3.amr.corp.intel.com/
> > [2] https://lore.kernel.org/linux-media/20171116003349.19235-2-laurent.pinchart+renesas@ideasonboard.com/
> 
> The UVC driver is violating the USB driver API [1] causing crashes and
> probably security vulnerabilities. It has to be fixed.
> 
> If there was a different way TODAY to do this, I would very happily
> implement it differently. But your patchset is 6 years old and Dan's 2
> and they have not landed. How many kernel versions is ok to put our
> users willingly at risk?
> 
> This patch simply serialises unregister_video? How can this patch
> affect the viability of your patchset or Dan's patch? If this patch is
> not needed in the future we can simply revert it.
> 
> When/If there is a better way to implement this, I would very happily
> send a follow-up patch to use that framework.

What I'm asking is that you, or someone else at your time, take over
these patches from Dan and myself and help with the huge backlog we have
in V4L2. You can't expect maintainers to fix everything in their spare
time. Helping there is a good way to lower the pressure on maintainers
and get patches reviewed more quickly.

> [1] https://www.kernel.org/doc/html/latest/driver-api/usb/callbacks.html#the-disconnect-callback
Ricardo Ribalda Nov. 22, 2023, 2:23 p.m. UTC | #3 
Hi Laurent

On Wed, 22 Nov 2023 at 15:04, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Ricardo,
>
> On Wed, Nov 22, 2023 at 02:59:31PM +0100, Ricardo Ribalda wrote:
> > On Wed, 22 Nov 2023 at 14:14, Laurent Pinchart wrote:
> > > On Wed, Nov 22, 2023 at 10:21:04AM +0000, Sakari Ailus wrote:
> > > > On Tue, Nov 21, 2023 at 07:53:50PM +0000, Ricardo Ribalda wrote:
> > > > > From: Guenter Roeck <linux@roeck-us.net>
> > > > >
> > > > > The call to uvc_disconnect() is not protected by any mutex.
> > > > > This means it can and will be called while other accesses to the video
> > > > > device are in progress. This can cause all kinds of race conditions,
> > > > > including crashes such as the following.
> > > > >
> > > > > usb 1-4: USB disconnect, device number 3
> > > > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> > > > > PGD 0 P4D 0
> > > > > Oops: 0000 [#1] PREEMPT SMP PTI
> > > > > CPU: 0 PID: 5633 Comm: V4L2CaptureThre Not tainted 4.19.113-08536-g5d29ca36db06 #1
> > > > > Hardware name: GOOGLE Edgar, BIOS Google_Edgar.7287.167.156 03/25/2019
> > > > > RIP: 0010:usb_ifnum_to_if+0x29/0x40
> > > > > Code: <...>
> > > > > RSP: 0018:ffffa46f42a47a80 EFLAGS: 00010246
> > > > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff904a396c9000
> > > > > RDX: ffff904a39641320 RSI: 0000000000000001 RDI: 0000000000000000
> > > > > RBP: ffffa46f42a47a80 R08: 0000000000000002 R09: 0000000000000000
> > > > > R10: 0000000000009975 R11: 0000000000000009 R12: 0000000000000000
> > > > > R13: ffff904a396b3800 R14: ffff904a39e88000 R15: 0000000000000000
> > > > > FS: 00007f396448e700(0000) GS:ffff904a3ba00000(0000) knlGS:0000000000000000
> > > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > > > CR2: 0000000000000000 CR3: 000000016cb46000 CR4: 00000000001006f0
> > > > > Call Trace:
> > > > >  usb_hcd_alloc_bandwidth+0x1ee/0x30f
> > > > >  usb_set_interface+0x1a3/0x2b7
> > > > >  uvc_video_start_transfer+0x29b/0x4b8 [uvcvideo]
> > > > >  uvc_video_start_streaming+0x91/0xdd [uvcvideo]
> > > > >  uvc_start_streaming+0x28/0x5d [uvcvideo]
> > > > >  vb2_start_streaming+0x61/0x143 [videobuf2_common]
> > > > >  vb2_core_streamon+0xf7/0x10f [videobuf2_common]
> > > > >  uvc_queue_streamon+0x2e/0x41 [uvcvideo]
> > > > >  uvc_ioctl_streamon+0x42/0x5c [uvcvideo]
> > > > >  __video_do_ioctl+0x33d/0x42a
> > > > >  video_usercopy+0x34e/0x5ff
> > > > >  ? video_ioctl2+0x16/0x16
> > > > >  v4l2_ioctl+0x46/0x53
> > > > >  do_vfs_ioctl+0x50a/0x76f
> > > > >  ksys_ioctl+0x58/0x83
> > > > >  __x64_sys_ioctl+0x1a/0x1e
> > > > >  do_syscall_64+0x54/0xde
> > > > >
> > > > > usb_set_interface() should not be called after the USB device has been
> > > > > unregistered. However, in the above case the disconnect happened after
> > > > > v4l2_ioctl() was called, but before the call to usb_ifnum_to_if().
> > > > >
> > > > > Acquire various mutexes in uvc_unregister_video() to fix the majority
> > > > > (maybe all) of the observed race conditions.
> > > > >
> > > > > The uvc_device lock prevents races against suspend and resume calls
> > > > > and the poll function.
> > > > >
> > > > > The uvc_streaming lock prevents races against stream related functions;
> > > > > for the most part, those are ioctls. This lock also requires other
> > > > > functions using this lock to check if a video device is still registered
> > > > > after acquiring it. For example, it was observed that the video device
> > > > > was already unregistered by the time the stream lock was acquired in
> > > > > uvc_ioctl_streamon().
> > > > >
> > > > > The uvc_queue lock prevents races against queue functions, Most of
> > > > > those are already protected by the uvc_streaming lock, but some
> > > > > are called directly. This is done as added protection; an actual race
> > > > > was not (yet) observed.
> > > > >
> > > > > Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > > > Cc: Alan Stern <stern@rowland.harvard.edu>
> > > > > Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> > > > > Reviewed-by: Tomasz Figa <tfiga@chromium.org>
> > > > > Reviewed-by: Sean Paul <seanpaul@chromium.org>
> > > > > Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> > > > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > > > ---
> > > > >  drivers/media/usb/uvc/uvc_driver.c | 9 +++++++++
> > > > >  1 file changed, 9 insertions(+)
> > > > >
> > > > > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> > > > > index 413c32867617..3408b865d346 100644
> > > > > --- a/drivers/media/usb/uvc/uvc_driver.c
> > > > > +++ b/drivers/media/usb/uvc/uvc_driver.c
> > > > > @@ -1907,14 +1907,22 @@ static void uvc_unregister_video(struct uvc_device *dev)
> > > > >  {
> > > > >     struct uvc_streaming *stream;
> > > > >
> > > > > +   mutex_lock(&dev->lock);
> > > > > +
> > > > >     list_for_each_entry(stream, &dev->streams, list) {
> > > > >             if (!video_is_registered(&stream->vdev))
> > > > >                     continue;
> > > > >
> > > > > +           mutex_lock(&stream->mutex);
> > > > > +           mutex_lock(&stream->queue.mutex);
> > > > > +
> > > > >             video_unregister_device(&stream->vdev);
> > > > >             video_unregister_device(&stream->meta.vdev);
> > > > >
> > > > >             uvc_debugfs_cleanup_stream(stream);
> > > > > +
> > > > > +           mutex_unlock(&stream->queue.mutex);
> > > > > +           mutex_unlock(&stream->mutex);
> > > > >     }
> > > > >
> > > > >     uvc_status_unregister(dev);
> > > > > @@ -1925,6 +1933,7 @@ static void uvc_unregister_video(struct uvc_device *dev)
> > > > >     if (media_devnode_is_registered(dev->mdev.devnode))
> > > > >             media_device_unregister(&dev->mdev);
> > > > >  #endif
> > > > > +   mutex_unlock(&dev->lock);
> > > > >  }
> > > > >
> > > > >  int uvc_register_video_device(struct uvc_device *dev,
> > > > >
> > > >
> > > > Instead of acquiring all the possible locks, could you instead take the
> > > > same approach as you do with ISP? It should use refcount_t btw.
> > > > <URL:https://chromium.googlesource.com/chromiumos/third_party/kernel/+/refs/heads/kcam-6.1/drivers/isp/isp-device.c:
> > >
> > > The right approach, as I've said countless of times, is to fix this at
> > > the cdev and V4L2 level. Dan Williams has done some ground work on this
> > > a while ago ([1]), and before that I posted an RFC series that
> > > overlapped with Dan's work (with a more naive and less efficient
> > > implementation of refcounting, see [2]).
> > >
> > > [1] https://lore.kernel.org/all/161117153776.2853729.6944617921517514510.stgit@dwillia2-desk3.amr.corp.intel.com/
> > > [2] https://lore.kernel.org/linux-media/20171116003349.19235-2-laurent.pinchart+renesas@ideasonboard.com/
> >
> > The UVC driver is violating the USB driver API [1] causing crashes and
> > probably security vulnerabilities. It has to be fixed.
> >
> > If there was a different way TODAY to do this, I would very happily
> > implement it differently. But your patchset is 6 years old and Dan's 2
> > and they have not landed. How many kernel versions is ok to put our
> > users willingly at risk?
> >
> > This patch simply serialises unregister_video? How can this patch
> > affect the viability of your patchset or Dan's patch? If this patch is
> > not needed in the future we can simply revert it.
> >
> > When/If there is a better way to implement this, I would very happily
> > send a follow-up patch to use that framework.
>
> What I'm asking is that you, or someone else at your time, take over
> these patches from Dan and myself and help with the huge backlog we have
> in V4L2. You can't expect maintainers to fix everything in their spare
> time. Helping there is a good way to lower the pressure on maintainers
> and get patches reviewed more quickly.

I do not think that this is a fair comment.
I am already reviewing all the uvc patches in the ML. Most of the time
in my spare time.
How much more help do you need there?

We know for over 4 years that there is a NULL deref issue in the uvc
driver. There is a 10 lines fix for it, that has been both reviewed
and tested.
What else is needed from a driver point of view?

It feels that by your position you are just pressuring to get a global
solution, that is a noble cause. But that is not the responsibility or
the role of a driver maintainer.

>
> > [1] https://www.kernel.org/doc/html/latest/driver-api/usb/callbacks.html#the-disconnect-callback
>
> --
> Regards,
>
> Laurent Pinchart
diff mbox series

Patch

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 413c32867617..3408b865d346 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -1907,14 +1907,22 @@  static void uvc_unregister_video(struct uvc_device *dev)
 {
 	struct uvc_streaming *stream;
 
+	mutex_lock(&dev->lock);
+
 	list_for_each_entry(stream, &dev->streams, list) {
 		if (!video_is_registered(&stream->vdev))
 			continue;
 
+		mutex_lock(&stream->mutex);
+		mutex_lock(&stream->queue.mutex);
+
 		video_unregister_device(&stream->vdev);
 		video_unregister_device(&stream->meta.vdev);
 
 		uvc_debugfs_cleanup_stream(stream);
+
+		mutex_unlock(&stream->queue.mutex);
+		mutex_unlock(&stream->mutex);
 	}
 
 	uvc_status_unregister(dev);
@@ -1925,6 +1933,7 @@  static void uvc_unregister_video(struct uvc_device *dev)
 	if (media_devnode_is_registered(dev->mdev.devnode))
 		media_device_unregister(&dev->mdev);
 #endif
+	mutex_unlock(&dev->lock);
 }
 
 int uvc_register_video_device(struct uvc_device *dev,