Hi Dan,
On 2/7/22 12:34, Dan Carpenter wrote:
> [ This code is older, but it showed up as a new warning because of
> moving the files around - dan ]
>
> Hello Hans Verkuil,
>
> The patch 71c689dc2e73: "media: v4l2-ctrls: split up into four source
> files" from Apr 27, 2021, leads to the following Smatch static
> checker warning:
>
> drivers/media/v4l2-core/v4l2-ctrls-api.c:374 v4l2_g_ext_ctrls_common() warn: uncapped user size for kvmalloc() will WARN
> drivers/media/v4l2-core/v4l2-ctrls-api.c:545 try_set_ext_ctrls_common() warn: uncapped user size for kvmalloc() will WARN
>
> drivers/media/v4l2-core/v4l2-ctrls-api.c
> 351 int v4l2_g_ext_ctrls_common(struct v4l2_ctrl_handler *hdl,
> 352 struct v4l2_ext_controls *cs,
> 353 struct video_device *vdev)
> 354 {
> 355 struct v4l2_ctrl_helper helper[4];
> 356 struct v4l2_ctrl_helper *helpers = helper;
> 357 int ret;
> 358 int i, j;
> 359 bool is_default, is_request;
> 360
> 361 is_default = (cs->which == V4L2_CTRL_WHICH_DEF_VAL);
> 362 is_request = (cs->which == V4L2_CTRL_WHICH_REQUEST_VAL);
> 363
> 364 cs->error_idx = cs->count;
> 365 cs->which = V4L2_CTRL_ID2WHICH(cs->which);
> 366
> 367 if (!hdl)
> 368 return -EINVAL;
> 369
> 370 if (cs->count == 0)
> 371 return class_check(hdl, cs->which);
> 372
> 373 if (cs->count > ARRAY_SIZE(helper)) {
> --> 374 helpers = kvmalloc_array(cs->count, sizeof(helper[0]),
>
> These days if "cs->count" is larger than INT_MAX it will trigger a
> WARN() because basically "people shouldn't be so trusting of user
> space". kvmalloc() used to be able to allocate more than INT_MAX but
> that led to integer overflow problmes and security bugs.
>
> This "cs->count" value comes from the user via the ioctl. I don't know
> what a sensible upper bound is though.
cs->count is capped to 1024 in drivers/media/v4l2-core/v4l2-ioctl.c.
Search for V4L2_CID_MAX_CTRLS.
There is no way for smatch to know this of course.
Regards,
Hans
>
> 375 GFP_KERNEL);
> 376 if (!helpers)
> 377 return -ENOMEM;
> 378 }
> 379
>
> regards,
> dan carpenter
