On Mon, 2016-03-14 at 08:21 +0100, Hans Verkuil wrote:

quoted

On 03/14/2016 08:12 AM, tiffany lin wrote:

quoted

Hi Hans,

After change to use "v4l-utils.git master branch", "V4l2-compliance
-d /dev/video1" fail on "fail: v4l2-test-buffers.cpp(555):
check_0(crbufs.reserved, sizeof(crbufs.reserved))".

Check the source code and found

	memset(&crbufs, 0xff, sizeof(crbufs));   -> crbufs to 0xff
        node->g_fmt(crbufs.format, i);
        crbufs.count = 0;
        crbufs.memory = m;
        fail_on_test(doioctl(node, VIDIOC_CREATE_BUFS, &crbufs));   
        fail_on_test(check_0(crbufs.reserved, sizeof(crbufs.reserved)));
        fail_on_test(crbufs.index != q.g_buffers());

crbufs is initialized to fill with 0xff and after VIDIOC_CREATE_BUFS,
crbufs.reserved field should be 0x0. But v4l2_m2m_create_bufs and
vb2_create_bufs do not process reserved filed.
Do we really need to check reserved filed filled with 0x0? Or we need to
change vb2_create_bufs to fix this issue?

The reserved field is zeroed in v4l_create_bufs() in v4l2-ioctl.c, so even before
vb2_create_bufs et al is called.

The fact that it is no longer zeroed afterwards suggests that someone is messing
with the reserved field.

You'll have to do a bit more digging, I'm afraid.

Hi Hans,

Thanks for your information.
I found the root cause is in "put_v4l2_create32".
It do not copy reserved field from kernel space to user space.
After modification,"test VIDIOC_REQBUFS/CREATE_BUFS/QUERYBUF: OK"

diff --git a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c

b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
index f38c076..109f687 100644

--- a/drivers/media/v4l2-core/v4l2-compat-ioctl32.c
+++ b/drivers/media/v4l2-core/v4l2-compat-ioctl32.c

@@ -280,7 +280,8 @@ static int put_v4l2_format32(struct v4l2_format *kp,

struct v4l2_format32 __user
 static int put_v4l2_create32(struct v4l2_create_buffers *kp, struct
v4l2_create_buffers32 __user *up)
 {
        if (!access_ok(VERIFY_WRITE, up, sizeof(struct
v4l2_create_buffers32)) ||
-           copy_to_user(up, kp, offsetof(struct v4l2_create_buffers32,
format)))
+           copy_to_user(up, kp, offsetof(struct v4l2_create_buffers32,
format)) ||
+           copy_to_user(up->reserved, kp->reserved,
sizeof(kp->reserved)))
                return -EFAULT;
        return __put_v4l2_format32(&kp->format, &up->format);
 }