[3.11.y.z extended stable] Patch "[media] V4L2: fix VIDIOC_CREATE_BUFS in 64- / 32-bit compatibility mode" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Fri May 30 09:28:56 UTC 2014

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

    [media] V4L2: fix VIDIOC_CREATE_BUFS in 64- / 32-bit compatibility mode

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:


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

For more information about the 3.11.y.z tree, see



>From c367a3b6491336d1ed5a4d0b49bf5af6bbafd79d Mon Sep 17 00:00:00 2001
From: Guennadi Liakhovetski <g.liakhovetski at gmx.de>
Date: Sat, 26 Apr 2014 12:51:31 -0300
Subject: [media] V4L2: fix VIDIOC_CREATE_BUFS in 64- / 32-bit compatibility

commit 97d9d23dda6f37d90aefeec4ed619d52df525382 upstream.

If a struct contains 64-bit fields, it is aligned on 64-bit boundaries
within containing structs in 64-bit compilations. This is the case with
struct v4l2_window, which contains pointers and is embedded into struct
v4l2_format, and that one is embedded into struct v4l2_create_buffers.
Unlike some other structs, used as a part of the kernel ABI as ioctl()
arguments, that are packed, these structs aren't packed. This isn't a
problem per se, but the ioctl-compat code for VIDIOC_CREATE_BUFS contains
a bug, that triggers in such 64-bit builds. That code wrongly assumes,
that in struct v4l2_create_buffers, struct v4l2_format immediately follows
the __u32 memory field, which in fact isn't the case. This bug wasn't
visible until now, because until recently hardly any applications used
this ioctl() and mostly embedded 32-bit only drivers implemented it. This
is changing now with addition of this ioctl() to some USB drivers, e.g.
UVC. This patch fixes the bug by copying parts of struct
v4l2_create_buffers separately.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski at gmx.de>
Acked-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab at samsung.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
 drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
index b63a5e584aa0..fca336b65351 100644
--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
@@ -178,6 +178,9 @@ struct v4l2_create_buffers32 {

 static int __get_v4l2_format32(struct v4l2_format *kp, struct v4l2_format32 __user *up)
+	if (get_user(kp->type, &up->type))
+		return -EFAULT;
 	switch (kp->type) {
@@ -204,17 +207,16 @@ static int __get_v4l2_format32(struct v4l2_format *kp, struct v4l2_format32 __us

 static int get_v4l2_format32(struct v4l2_format *kp, struct v4l2_format32 __user *up)
-	if (!access_ok(VERIFY_READ, up, sizeof(struct v4l2_format32)) ||
-			get_user(kp->type, &up->type))
-			return -EFAULT;
+	if (!access_ok(VERIFY_READ, up, sizeof(struct v4l2_format32)))
+		return -EFAULT;
 	return __get_v4l2_format32(kp, up);

 static int get_v4l2_create32(struct v4l2_create_buffers *kp, struct v4l2_create_buffers32 __user *up)
 	if (!access_ok(VERIFY_READ, up, sizeof(struct v4l2_create_buffers32)) ||
-	    copy_from_user(kp, up, offsetof(struct v4l2_create_buffers32, format.fmt)))
-			return -EFAULT;
+	    copy_from_user(kp, up, offsetof(struct v4l2_create_buffers32, format)))
+		return -EFAULT;
 	return __get_v4l2_format32(&kp->format, &up->format);


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