[PATCH 3.13 029/105] [media] v4l2-common: fix overflow in v4l_bound_align_image()

Kamal Mostafa
2014-10-27T19:03:36Z

From: Maciej Matraszek <m.matraszek@samsung.com>

commit 3bacc10cd4a85bc70bc0b6c001d3bf995c7fe04c upstream.

Fix clamp_align() used in v4l_bound_align_image() to prevent overflow
when passed large value like UINT32_MAX.

In the current implementation:
clamp_align(UINT32_MAX, 8, 8192, 3)

returns 8, because in line:

x = (x + (1 << (align - 1))) & mask;

x overflows to (-1 + 4) & 0x7 = 3, while expected value is 8192.

v4l_bound_align_image() is heavily used in VIDIOC_S_FMT and
VIDIOC_SUBDEV_S_FMT ioctls handlers, and documentation of the latter
explicitly states that:

"The modified format should be as close as possible to the original
request."
-- http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-subdev-g-fmt.html

Thus one would expect, that passing UINT32_MAX as format width and
height will result in setting maximum possible resolution for the
device. Particularly, when the driver doesn't support
VIDIOC_ENUM_FRAMESIZES ioctl, which is common in the codebase.

Fixes changeset: b0d3159be9a3

Signed-off-by: Maciej Matraszek <m.matraszek@samsung.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/media/v4l2-core/v4l2-common.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
index 433d6d7..c5521ce 100644
--- a/drivers/media/v4l2-core/v4l2-common.c
+++ b/drivers/media/v4l2-core/v4l2-common.c
@@ -431,16 +431,13 @@ static unsigned int clamp_align(unsigned int x, unsigned int min,
/* Bits that must be zero to be aligned */
unsigned int mask = ~((1 << align) - 1);

+ /* Clamp to aligned min and max */
+ x = clamp(x, (min + ~mask) & mask, max & mask);
+
/* Round to nearest aligned value */
if (align)
x = (x + (1 << (align - 1))) & mask;

- /* Clamp to aligned value of min and max */
- if (x < min)
- x = (min + ~mask) & mask;
- else if (x > max)
- x = max & mask;
-
return x;
}

--
1.9.1