On Tue, Sep 18, 2012 at 10:24:55AM +0100, Ian Abbott wrote: > On 2012-09-18 01:17, H Hartley Sweeten wrote: > >The 'chanlist' in the comedi_cmd struct is an unsigned int __user > >pointer. > > > >The do_cmd_ioctl() and do_cmdtest_ioctl() functions in comedi_fops > >do a copy_from_user() to move the data from user space to kernel > >space before passing the comedi_cmd to the comedi drivers. > > > >Unfortunately, the drivers then think 'chanlist' is still a > >__user pointer since thats how the struct is defined. > > > >Make the 'chanlist' a union of both a __user and kernel pointer. > >The do_cmd_*_ioctl() functions are the only ones that use the > >__user pointer. All the drivers then use the kernel pointer to > >access the chanlist. > > Personally, I'd rather get rid of the __user pointers in comedi.h > and do the appropriate casting in the comedi core. > > (I came up with a macro a while ago to make the casting less ugly, > but I need to test that with `sparse` to make sure it doesn't get > confused.) I didn't like that macro at all. :( Casting away user pointers should be something that is only done rarely and it's good if it's something you have to think about. regards, dan carpenter _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
