get data to user space from kernel

[sebastien person]

Hi,

I have a network driver that get specific informations from device
but I can't envisage the size of the informations. So I do a kmalloc
call when data come.

But my problem seems to come from the kmalloc because when I try to
send data to user space via an ioctl call I get a segmentation fault.

One solution would be to pass fixed size beetween the both but it 
isn't the cleaner.

I've heard about copy_to_user method , is it the best way ?
Is there a way to create a struct in user space dynamicaly from kernel
space ?

thanks for any help ...

sebastien person