[PATCH v3 0/3] media: uvcvideo: harden the frame buffer size computation

[Natasha Klaus <natalie.klaus@runtimeverification.com>]

uvc_parse_frame() recomputes dwMaxVideoFrameBufferSize for uncompressed
formats from three descriptor fields that nothing validates. The product
is evaluated in 32-bit signed arithmetic, so it wraps, and the driver
stores a size that is usually far too small and sometimes exactly zero.

Noam Ben Shimon reported and fixed the overflow. Reviewing it surfaced a
second route to a zero size, and Ricardo Ribalda asked for a series
rather than two independent patches, so the two cases are not handled
inconsistently.

  1/3  changes the return convention of uvc_parse_frame() so it can
       report "skip this frame descriptor" separately from a fatal
       error. Suggested by Ricardo.
  2/3  Noam's overflow check, adapted to skip rather than reject, with
       DIV_ROUND_UP_ULL and the operand values in the diagnostic per David
       Laight's review.
  3/3  the zero-size case.

On stable: 1/3 carries Cc: stable with no Fixes: tag of its own. It is a
prerequisite, since 2/3 and 3/3 need -EINVAL to mean "skip". Backporting
2/3 without 1/3 is not broken, it reverts to discarding the streaming
interface, but the commit message would then describe something the
backport does not do. Both or neither, please.

Carrying 2/3 on Noam's behalf, with his agreement on the list.

Tested by Noam on a UVC gadget over dummy_hcd: a format with an
over-U32_MAX frame, a zero-size frame and a valid one, where both bad
frames are skipped and parsing continues to the good one. The -ENODATA
truncated-descriptor path and 32-bit code generation are not covered.

Changes in v3:
- Tested-by from Noam Ben Shimon added to all three

Changes in v2:
- 1/3: check -ENODATA before counting the frame (Ricardo Ribalda)
- 2/3: DIV_ROUND_UP -> DIV_ROUND_UP_ULL (Ricardo Ribalda)
- Reviewed-by from Ricardo Ribalda added to all three

Natasha Klaus (2):
  media: uvcvideo: Let uvc_parse_frame() report a skipped frame
  media: uvcvideo: Skip frame descriptors with a zero computed size

Noam Ben Shimon (1):
  media: uvcvideo: Fix integer overflow in frame buffer size calculation

 drivers/media/usb/uvc/uvc_driver.c | 52 ++++++++++++++++++++++--------
 1 file changed, 39 insertions(+), 13 deletions(-)

-- 
2.34.1