[PATCH v3] usb: gadget: uvc: Fix crash when encoding data for usb request

From: Dan Vacura <w36195@motorola.com>
To: linux-usb@vger.kernel.org
Cc: Dan Vacura <w36195@motorola.com>,
	stable@vger.kernel.org,
	Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Felipe Balbi <balbi@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Bhupesh Sharma <bhupesh.sharma@st.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v3] usb: gadget: uvc: Fix crash when encoding data for usb request
Date: Thu, 31 Mar 2022 13:40:23 -0500	[thread overview]
Message-ID: <20220331184024.23918-1-w36195@motorola.com> (raw)

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buf_used) of the active buffer (no longer
active) is not reset.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")
Cc: <stable@vger.kernel.org>
Signed-off-by: Dan Vacura <w36195@motorola.com>

---
Changes in v3:
- Cc stable
Changes in v2:
- Add Fixes tag

 drivers/usb/gadget/function/uvc_queue.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/gadget/function/uvc_queue.c b/drivers/usb/gadget/function/uvc_queue.c
index d852ac9e47e7..2cda982f3765 100644
--- a/drivers/usb/gadget/function/uvc_queue.c
+++ b/drivers/usb/gadget/function/uvc_queue.c
@@ -264,6 +264,8 @@ void uvcg_queue_cancel(struct uvc_video_queue *queue, int disconnect)
 		buf->state = UVC_BUF_STATE_ERROR;
 		vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_ERROR);
 	}
+	queue->buf_used = 0;
+
 	/* This must be protected by the irqlock spinlock to avoid race
 	 * conditions between uvc_queue_buffer and the disconnection event that
 	 * could result in an interruptible wait in uvc_dequeue_buffer. Do not
-- 
2.32.0

