Re: [PATCH] v4l2: uvcvideo use after free bug fix

[Yang Ruirui]

----- Original message -----
> Hi,
> 
> On Tuesday 06 September 2011 15:02:54 Hans Verkuil wrote:
> > On Tuesday, September 06, 2011 14:12:14 Laurent Pinchart wrote:
> > > On Tuesday 06 September 2011 14:08:08 Dave Young wrote:
> > > > Reported-by: Sitsofe Wheeler <sitsofe@xxxxxxxxx>
> > > > Signed-off-by: Dave Young <hidave.darkstar@xxxxxxxxx>
> > > > Tested-by: Sitsofe Wheeler <sitsofe@xxxxxxxxx>
> > > > Acked-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > > > 
> > > > Unplugging uvc video camera trigger following oops:
> > > > 
> > > > eeepc kernel: [ 1393.500719] usb 3-2: USB disconnect, device
> > > > number 4 eeepc kernel: [ 1393.504351] uvcvideo: Failed to resubmit
> > > > video URB (-19). eeepc kernel: [ 1495.428853] BUG: unable to
> > > > handle kernel paging request at 6b6b6bcb eeepc kernel: [
> > > > 1495.429017] IP: [<b0358d37>]
> > > > dev_get_drvdata+0x17/0x20 eeepc kernel: [ 1495.429017] *pde =
> > > > 00000000 eeepc kernel: [ 1495.429017] Oops: 0000 [#1]
> > > > DEBUG_PAGEALLOC eeepc kernel: [ 1495.429017]
> > > > eeepc kernel: [ 1495.429017] Pid: 3476, comm: cheese Not tainted
> > > > 3.1.0-rc3-00270-g7a54f5e-dirty #485 ASUSTeK Computer INC. 900/900
> > > > eeepc kernel: [ 1495.429017] EIP: 0060:[<b0358d37>] EFLAGS:
> > > > 00010202 CPU: 0 eeepc kernel: [ 1495.429017] EIP is at
> > > > dev_get_drvdata+0x17/0x20 eeepc kernel: [ 1495.429017] EAX:
> > > > 6b6b6b6b EBX: eb08d870 ECX: 00000000 EDX: eb08d930 eeepc kernel: [
> > > > 1495.429017] ESI: eb08d870 EDI: eb08d870 EBP: d3249cac ESP:
> > > > d3249cac eeepc kernel: [ 1495.429017]Â  DS: 007b ES: 007b FS: 0000
> > > > GS: 00e0 SS: 0068 eeepc kernel: [ 1495.429017] Process cheese
> > > > (pid: 3476, ti=d3248000 task=df46d870 task.ti=d3248000) eeepc
> > > > kernel: [ 1495.429017] Stack: eeepc kernel: [ 1495.429017] 
> > > > d3249cb8 b03e77a1 d307b840 d3249ccc b03e77d1 d307b840 eb08d870
> > > > eb08d830 eeepc kernel: [ 1495.429017]Â  d3249ce4 b03ed3b7 00000246
> > > > d307b840 eb08d870 d3021b80 d3249cec b03ed565 eeepc kernel: [
> > > > 1495.429017]Â  d3249cfc b03e044d e8323d10 b06e013c d3249d18
> > > > b0355fb9 fffffffe d3249d1c eeepc kernel: [ 1495.429017] Call Trace:
> > > > eeepc kernel: [ 1495.429017]Â  [<b03e77a1>]
> > > > v4l2_device_disconnect+0x11/0x30 eeepc kernel: [ 1495.429017] 
> > > > [<b03e77d1>] v4l2_device_unregister+0x11/0x50 eeepc kernel: [
> > > > 1495.429017]Â  [<b03ed3b7>] uvc_delete+0x37/0x110 eeepc kernel: [
> > > > 1495.429017]Â  [<b03ed565>] uvc_release+0x25/0x30 eeepc kernel: [
> > > > 1495.429017]Â  [<b03e044d>] v4l2_device_release+0x9d/0xc0 eeepc
> > > > kernel: [ 1495.429017]Â  [<b0355fb9>] device_release+0x19/0x90
> > > > eeepc kernel: [ 1495.429017]Â  [<b03adfdc>] ?
> > > > usb_hcd_unlink_urb+0x7c/0x90 eeepc kernel: [ 1495.429017] 
> > > > [<b026b99c>] kobject_release+0x3c/0x90 eeepc kernel: [
> > > > 1495.429017]Â  [<b026b960>] ? kobject_del+0x30/0x30 eeepc kernel: [
> > > > 1495.429017]Â  [<b026ca4c>] kref_put+0x2c/0x60 eeepc kernel: [
> > > > 1495.429017]Â  [<b026b88d>] kobject_put+0x1d/0x50 eeepc kernel: [
> > > > 1495.429017]Â  [<b03b2385>] ? usb_autopm_put_interface+0x25/0x30
> > > > eeepc kernel: [ 1495.429017] [<b03f0e5d>] ?
> > > > uvc_v4l2_release+0x5d/0xd0 eeepc kernel: [ 1495.429017]
> > > > [<b0355d2f>] put_device+0xf/0x20 eeepc kernel: [ 1495.429017] 
> > > > [<b03dfa96>] v4l2_release+0x56/0x60 eeepc kernel: [ 1495.429017] 
> > > > [<b019c8dc>] fput+0xcc/0x220 eeepc kernel: [ 1495.429017] 
> > > > [<b01990f4>] filp_close+0x44/0x70 eeepc kernel: [ 1495.429017] 
> > > > [<b012b238>] put_files_struct+0x158/0x180 eeepc kernel: [
> > > > 1495.429017]Â  [<b012b100>] ? put_files_struct+0x20/0x180 eeepc
> > > > kernel: [ 1495.429017]Â  [<b012b2a0>] exit_files+0x40/0x50 eeepc
> > > > kernel: [ 1495.429017]Â  [<b012b9e7>] do_exit+0x5a7/0x660 eeepc
> > > > kernel: [ 1495.429017]Â  [<b0135f72>] ? __dequeue_signal+0x12/0x120
> > > > eeepc kernel: [ 1495.429017]Â  [<b055edf2>] ?
> > > > _raw_spin_unlock_irq+0x22/0x30 eeepc kernel: [ 1495.429017] 
> > > > [<b012badc>] do_group_exit+0x3c/0xb0 eeepc kernel: [ 1495.429017] 
> > > > [<b015792b>] ? trace_hardirqs_on+0xb/0x10 eeepc kernel: [
> > > > 1495.429017] [<b013755f>] get_signal_to_deliver+0x18f/0x570 eeepc
> > > > kernel: [ 1495.429017] [<b01020f7>] do_signal+0x47/0x9e0
> > > > eeepc kernel: [ 1495.429017]Â  [<b055edf2>] ?
> > > > _raw_spin_unlock_irq+0x22/0x30 eeepc kernel: [ 1495.429017] 
> > > > [<b015792b>] ? trace_hardirqs_on+0xb/0x10 eeepc kernel: [
> > > > 1495.429017] [<b0123300>] ? T.1034+0x30/0xc0
> > > > eeepc kernel: [ 1495.429017]Â  [<b055c45f>] ? schedule+0x29f/0x640
> > > > eeepc kernel: [ 1495.429017]Â  [<b0102ac8>]
> > > > do_notify_resume+0x38/0x40 eeepc kernel: [ 1495.429017] 
> > > > [<b055f154>] work_notifysig+0x9/0x11 eeepc kernel: [ 1495.429017]
> > > > Code: e5 5d 83 f8 01 19 c0 f7 d0 83 e0 f0 c3 8d b4 26 00 00 00 00
> > > > 55 85 c0 89 e5 75 09 31 c0 5d c3 90 8d 74 26 00 8b 40 04 85 c0 74
> > > > f0 <8b> 40 60 5d c3 8d 74 26 00 55 89 e5 53 89 c3 83 ec 04 8b 40
> > > > 04 eeepc kernel: [ 1495.429017] EIP: [<b0358d37>]
> > > > dev_get_drvdata+0x17/0x20 SS:ESP 0068:d3249cac eeepc kernel: [
> > > > 1495.429017] CR2: 000000006b6b6bcb eeepc kernel: [ 1495.466975]
> > > > uvcvideo: Failed to resubmit video URB (-27). eeepc kernel: [
> > > > 1495.467860] uvcvideo: Failed to resubmit video URB (-27). eeepc
> > > > kernel: last message repeated 3 times eeepc kernel: [ 1495.512610]
> > > > ---[ end trace 73ec16848794e5a5 ]---
> > > > 
> > > > For uvc device, dev->vdev.dev is the &intf->dev,
> > > > 
> > > > uvc_delete code is as below:
> > > > ÂÂÂ usb_put_intf(dev->intf);
> > > > ÂÂÂ usb_put_dev(dev->udev);
> > > > ÂÂÂ
> > > > ÂÂÂ uvc_status_cleanup(dev);
> > > > ÂÂÂ uvc_ctrl_cleanup_device(dev);
> > > > 
> > > > ## the intf dev is released above, so below code will oops.
> > > > 
> > > > ÂÂÂ if (dev->vdev.dev)
> > > > ÂÂÂ
> > > > ÂÂÂ ÂÂÂ v4l2_device_unregister(&dev->vdev);
> > > > 
> > > > Fix it by get_device in v4l2_device_register and put_device in
> > > > v4l2_device_disconnect ---
> > > > 
> > > > drivers/media/video/v4l2-device.c |Â Â Â  2 ++
> > > > 1 file changed, 2 insertions(+)
> > > > 
> > > > diff --git a/drivers/media/video/v4l2-device.c
> > > > b/drivers/media/video/v4l2-device.c index c72856c..e6a2c3b 100644
> > > > --- a/drivers/media/video/v4l2-device.c
> > > > +++ b/drivers/media/video/v4l2-device.c
> > > > @@ -38,6 +38,7 @@ int v4l2_device_register(struct device *dev,
> > > > struct v4l2_device *v4l2_dev) mutex_init(&v4l2_dev->ioctl_lock);
> > > > 
> > > > ÂÂÂ v4l2_prio_init(&v4l2_dev->prio);
> > > > ÂÂÂ kref_init(&v4l2_dev->ref);
> > > > 
> > > > +ÂÂÂ get_device(dev);
> > > > 
> > > > ÂÂÂ v4l2_dev->dev = dev;
> > > 
> > > We store a reference to the device in v4l2_dev, and we use it later.
> > > We thus need either get a reference to the device (like done by this
> > > patch), or mandate drivers not to release their reference to the
> > > device before calling v4l2_device_unregister and/or
> > > v4l2_device_disconnect (in this case that would mean moving the
> > > usb_put_intf call after the v4l2_device_unregister call in the
> > > uvcvideo driver).
> > > 
> > > Do you have a preference ?
> > 
> > My preference would be to get a reference ourselves,
> 
> Sounds good to me.
> 
> > but I don't have the time to fully analyze this. So I leave that to
> > you.
> 
> I will pick the patch and push it to v3.1. Dave, your patch fixes a
> problem  that is not UVC-specific. Do you mind if I rephrase the (pretty
> verbose)Â  commit message to explain the v4l issue instead ?

It's fine for me, thank you.

> 
> Hans, can I get your SoB line for
> 
> From face69e36b00c0e461a4b894f46213091515defd Mon Sep 17 00:00:00 2001
> From: Hans Verkuil <hverkuil@xxxxxxxxx>
> Date: Tue, 6 Sep 2011 15:23:18 +0200
> Subject: [PATCH] v4l: Fix use-after-free case in v4l2_device_release
> 
> Drivers that have no v4l2_device release callback might free the
> v4l2_device instance in the video_device release callback. Make sure we
> don't access the v4l2_device instance after it gets freed.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
>Â  drivers/media/video/v4l2-dev.c |Â Â  11 +++++++++++
>Â  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/media/video/v4l2-dev.c
> b/drivers/media/video/v4l2-dev.c index 06f1400..d721565 100644
> --- a/drivers/media/video/v4l2-dev.c
> +++ b/drivers/media/video/v4l2-dev.c
> @@ -173,6 +173,17 @@ static void v4l2_device_release(struct device *cd)
>Â  ÂÂÂ ÂÂÂ media_device_unregister_entity(&vdev->entity);
>Â  #endif
>Â  
> +ÂÂÂ /* Do not call v4l2_device_put if there is no release callback set.
> +ÂÂÂ  * Drivers that have no v4l2_device release callback might free the
> +ÂÂÂ  * v4l2_dev instance in the video_device release callback below, so we
> +ÂÂÂ  * must perform this check here.
> +ÂÂÂ  *
> +ÂÂÂ  * TODO: In the long run all drivers that use v4l2_device should use
> the +ÂÂÂ  * v4l2_device release callback. This check will then be
> unnecessary. +ÂÂÂ  */
> +ÂÂÂ if (v4l2_dev->release == NULL)
> +ÂÂÂ ÂÂÂ v4l2_dev = NULL;
> +
>Â  ÂÂÂ /* Release video_device and perform other
>Â  ÂÂÂ Â Â  cleanups as needed. */
>Â  ÂÂÂ vdev->release(vdev);
> -- 
> 1.7.3.4
> 
> -- 
> Regards,
> 
> Laurent Pinchart

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