[PATCH 5.14 051/432] media: uvc: dont do DMA on stack

Greg Kroah-Hartman
2021-09-16T17:14:21Z

From: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

commit 1a10d7fdb6d0e235e9d230916244cc2769d3f170 upstream.

As warned by smatch:
drivers/media/usb/uvc/uvc_v4l2.c:911 uvc_ioctl_g_input() error: doing dma on the stack (&i)
drivers/media/usb/uvc/uvc_v4l2.c:943 uvc_ioctl_s_input() error: doing dma on the stack (&i)

those two functions call uvc_query_ctrl passing a pointer to
a data at the DMA stack. those are used to send URBs via
usb_control_msg(). Using DMA stack is not supported and should
not work anymore on modern Linux versions.

So, use a kmalloc'ed buffer.

Cc: stable@vger.kernel.org # Kernel 4.9 and upper
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/media/usb/uvc/uvc_v4l2.c | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)

--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -899,8 +899,8 @@ static int uvc_ioctl_g_input(struct file
{
struct uvc_fh *handle = fh;
struct uvc_video_chain *chain = handle->chain;
+ u8 *buf;
int ret;
- u8 i;

if (chain->selector == NULL ||
(chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) {
@@ -908,22 +908,27 @@ static int uvc_ioctl_g_input(struct file
return 0;
}

+ buf = kmalloc(1, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR, chain->selector->id,
chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
- &i, 1);
- if (ret < 0)
- return ret;
+ buf, 1);
+ if (!ret)
+ *input = *buf - 1;

- *input = i - 1;
- return 0;
+ kfree(buf);
+
+ return ret;
}

static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input)
{
struct uvc_fh *handle = fh;
struct uvc_video_chain *chain = handle->chain;
+ u8 *buf;
int ret;
- u32 i;

ret = uvc_acquire_privileges(handle);
if (ret < 0)
@@ -939,10 +944,17 @@ static int uvc_ioctl_s_input(struct file
if (input >= chain->selector->bNrInPins)
return -EINVAL;

- i = input + 1;
- return uvc_query_ctrl(chain->dev, UVC_SET_CUR, chain->selector->id,
- chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
- &i, 1);
+ buf = kmalloc(1, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ *buf = input + 1;
+ ret = uvc_query_ctrl(chain->dev, UVC_SET_CUR, chain->selector->id,
+ chain->dev->intfnum, UVC_SU_INPUT_SELECT_CONTROL,
+ buf, 1);
+ kfree(buf);
+
+ return ret;
}

static int uvc_ioctl_queryctrl(struct file *file, void *fh,