Re: [PATCH v2] usb: gadget: uvc: Fix crash when encoding data for usb request

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Mar 18, 2022 at 11:47:06AM -0500, Dan Vacura wrote:
> During the uvcg_video_pump() process, if an error occurs and
> uvcg_queue_cancel() is called, the buffer queue will be cleared out, but
> the current marker (queue->buf_used) of the active buffer (no longer
> active) is not reset. On the next iteration of uvcg_video_pump() the
> stale buf_used count will be used and the logic of min((unsigned
> int)len, buf->bytesused - queue->buf_used) may incorrectly calculate a
> nbytes size, causing an invalid memory access.
> 
> [80802.185460][  T315] configfs-gadget gadget: uvc: VS request completed
> with status -18.
> [80802.185519][  T315] configfs-gadget gadget: uvc: VS request completed
> with status -18.
> ...
> uvcg_queue_cancel() is called and the queue is cleared out, but the
> marker queue->buf_used is not reset.
> ...
> [80802.262328][ T8682] Unable to handle kernel paging request at virtual
> address ffffffc03af9f000
> ...
> ...
> [80802.263138][ T8682] Call trace:
> [80802.263146][ T8682]  __memcpy+0x12c/0x180
> [80802.263155][ T8682]  uvcg_video_pump+0xcc/0x1e0
> [80802.263165][ T8682]  process_one_work+0x2cc/0x568
> [80802.263173][ T8682]  worker_thread+0x28c/0x518
> [80802.263181][ T8682]  kthread+0x160/0x170
> [80802.263188][ T8682]  ret_from_fork+0x10/0x18
> [80802.263198][ T8682] Code: a8c12829 a88130cb a8c130
> 
> Fixes: d692522577c0 ("usb: gadget/uvc: Port UVC webcam gadget to use videobuf2 framework")
> Signed-off-by: Dan Vacura <w36195@motorola.com>
> 
> ---
> Changes in v2:
> - Add Fixes tag

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>