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SubjectRe: [PATCH v2 14/19] [media] uvcvideo: prevent bounds-check bypass via speculative execution
Date
Hi Dan,

Thank you for the patch.

On Friday, 12 January 2018 02:47:40 EEST Dan Williams wrote:
> Static analysis reports that 'index' may be a user controlled value that
> is used as a data dependency to read 'pin' from the
> 'selector->baSourceID' array. In order to avoid potential leaks of
> kernel memory values, block speculative execution of the instruction
> stream that could issue reads based on an invalid value of 'pin'.
>
> Based on an original patch by Elena Reshetova.
>
> Laurent notes:
>
> "...as this is nowhere close to being a fast path, I think we can close
> this potential hole as proposed in the patch"
>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: linux-media@vger.kernel.org
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

What's the status of this series (and of this patch in particular) ?

> ---
> drivers/media/usb/uvc/uvc_v4l2.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c
> b/drivers/media/usb/uvc/uvc_v4l2.c index 3e7e283a44a8..30ee200206ee 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -22,6 +22,7 @@
> #include <linux/mm.h>
> #include <linux/wait.h>
> #include <linux/atomic.h>
> +#include <linux/nospec.h>
>
> #include <media/v4l2-common.h>
> #include <media/v4l2-ctrls.h>
> @@ -809,8 +810,12 @@ static int uvc_ioctl_enum_input(struct file *file, void
> *fh, const struct uvc_entity *selector = chain->selector;
> struct uvc_entity *iterm = NULL;
> u32 index = input->index;
> + __u8 *elem = NULL;
> int pin = 0;
>
> + if (selector)
> + elem = array_ptr(selector->baSourceID, index,
> + selector->bNrInPins);
> if (selector == NULL ||
> (chain->dev->quirks & UVC_QUIRK_IGNORE_SELECTOR_UNIT)) {
> if (index != 0)
> @@ -820,8 +825,8 @@ static int uvc_ioctl_enum_input(struct file *file, void
> *fh, break;
> }
> pin = iterm->id;
> - } else if (index < selector->bNrInPins) {
> - pin = selector->baSourceID[index];
> + } else if (elem) {
> + pin = *elem;
> list_for_each_entry(iterm, &chain->entities, chain) {
> if (!UVC_ENTITY_IS_ITERM(iterm))
> continue;

--
Regards,

Laurent Pinchart



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