Re: [linux-uvc-devel] [PATCH RESEND v3 0/5] media: uvcvideo: Fix race conditions

[Michael G. <mg...@pe...>]

Ping!

This series seems to be hanging around. It would be nice to get these
patches upstream, as they help my uvc-gadget workflow. Without them it
is likely that in the development cases my gadget won't start and then
leave the whole xhci controller broken.

@Laurent, what do you think?

Regards,
Michael


On Wed, Sep 16, 2020 at 07:25:42PM -0700, Guenter Roeck wrote:
>Something seems to have gone wrong with v3 of this patch series.
>I am sure I sent it out, but I don't find it anywhere.
>Resending. Sorry for any duplicates.
>
>The uvcvideo code has no lock protection against USB disconnects
>while video operations are ongoing. This has resulted in random
>error reports, typically pointing to a crash in usb_ifnum_to_if(),
>called from usb_hcd_alloc_bandwidth(). A typical traceback is as
>follows.
>
>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
>
>While there are not many references to this problem on mailing lists, it is
>reported on a regular basis on various Chromebooks (roughly 300 reports
>per month). The problem is relatively easy to reproduce by adding msleep()
>calls into the code.
>
>I tried to reproduce the problem with non-uvcvideo webcams, but was
>unsuccessful. I was unable to get Philips (pwc) webcams to work. gspca
>based webcams don't experience the problem, or at least I was unable to
>reproduce it (The gspa driver does not trigger sending USB messages in the
>open function, and otherwise uses the locking mechanism provided by the
>v4l2/vb2 core).
>
>I don't presume to claim that I found every issue, but this patch series
>should fix at least the major problems.
>
>The patch series was tested exensively on a Chromebook running chromeos-4.19
>and on a Linux system running a v5.8.y based kernel.
>
>v3:
>- In patch 5/5, add missing calls to usb_autopm_put_interface() and kfree()
>  to failure code path
>
>v2:
>- Added details about problem frequency and testing with non-uvc webcams
>  to summary
>- In patch 4/5, return EPOLLERR instead of -ENODEV on poll errors
>- Fix description in patch 5/5
>
>----------------------------------------------------------------
>Guenter Roeck (5):
>      media: uvcvideo: Cancel async worker earlier
>      media: uvcvideo: Lock video streams and queues while unregistering
>      media: uvcvideo: Release stream queue when unregistering video device
>      media: uvcvideo: Protect uvc queue file operations against disconnect
>      media: uvcvideo: Abort uvc_v4l2_open if video device is unregistered
>
> drivers/media/usb/uvc/uvc_ctrl.c   | 11 ++++++----
> drivers/media/usb/uvc/uvc_driver.c | 12 ++++++++++
> drivers/media/usb/uvc/uvc_queue.c  | 32 +++++++++++++++++++++++++--
> drivers/media/usb/uvc/uvc_v4l2.c   | 45 ++++++++++++++++++++++++++++++++++++--
> drivers/media/usb/uvc/uvcvideo.h   |  1 +
> 5 files changed, 93 insertions(+), 8 deletions(-)

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