[3.16.y-ckt stable] Patch "[media] v4l2-common: fix overflow in v4l_bound_align_image()" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    [media] v4l2-common: fix overflow in v4l_bound_align_image()

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From b0cf446b37d700befdabe33cf695a181c64686fa Mon Sep 17 00:00:00 2001
From: Maciej Matraszek <m.matraszek at samsung.com>
Date: Mon, 15 Sep 2014 05:14:48 -0300
Subject: [media] v4l2-common: fix overflow in v4l_bound_align_image()

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 at samsung.com>
Acked-by: Sakari Ailus <sakari.ailus at linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab at osg.samsung.com>
Signed-off-by: Luis Henriques <luis.henriques at 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 433d6d77942e..c5521cec933b 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;
 }

--
2.1.0