[PATCH v2] media: uvc: don't do DMA on stack

Mauro Carvalho Chehab
2021-06-21T13:23:41Z

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 temporary buffer, allocated together with
struct uvc_video_chain.

Cc: stable@vger.kernel.org # Kernel 4.9 and upper
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
drivers/media/usb/uvc/uvc_v4l2.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index 252136cc885c..d680ae8a5f87 100644
--- 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 *file, void *fh, unsigned int *input)
{
struct uvc_fh *handle = fh;
struct uvc_video_chain *chain = handle->chain;
+ char *buf;
int ret;
- u8 i;

if (chain->selector == NULL ||
(chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) {
@@ -908,13 +908,18 @@ static int uvc_ioctl_g_input(struct file *file, void *fh, unsigned int *input)
return 0;
}

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

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

@@ -922,8 +927,8 @@ 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;
+ char *buf;
int ret;
- u32 i;

ret = uvc_acquire_privileges(handle);
if (ret < 0)
@@ -939,10 +944,15 @@ static int uvc_ioctl_s_input(struct file *file, void *fh, unsigned int input)
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);
+
+ *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,
--
2.31.1