Re: [PATCH v2 2/2] ppdev: add support for compat ioctl

[Sudip Mukherjee]

On Fri, Dec 18, 2015 at 12:12:05AM +0100, Arnd Bergmann wrote:
> On Thursday 17 December 2015 17:58:52 Bamvor Jian Zhang wrote:
> > The arg of ioctl in ppdev is the pointer of integer except the
> > timeval in PPSETTIME, PPGETTIME. Different size of timeval
> > is already supported by the previous patches. So, it is safe
> > to add compat support.
> > 
> > Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@xxxxxxxxxx>
> > 
> 
> Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>
> 
> (I think I replied with the reviewed-by tag before to this patch)

I was testing this series today. And it is breaking my userspace code. I
am attaching my userspace code for you to check. Its very simple
userspace code:
1: open
2: ioctl to claim
3: ioctl - PPGETTIME
4: ioctl - PPSETTIME
5: ioctl - PPGETTIME
6: ioctl - release
7: close

Without this series it works as expected.

With this series applied, the userspace code prints the error message:
PPNEGOT: Bad address

I traced it with strace and:
ioctl(3, PPGETTIME, 0xbfe91508)         = -1 EFAULT (Bad address)

regards
sudip
#include <stdio.h>
#include<stdlib.h>
#include <unistd.h>
#include <linux/ioctl.h>
#include <linux/parport.h>
#include <linux/ppdev.h>
#include <fcntl.h>
#include <sys/time.h>

int main(int argc, char *argv[])
{
  int fd
  struct timeval tv;	

  fd = open("/dev/parport0",O_RDWR);
  if (fd == -1)
  {
    perror("open");
    exit(1);
  }
  if (ioctl(fd,PPCLAIM))
  {
    perror("PPCLAIM");
    close(fd);
    exit(1);
  }
  if (ioctl(fd, PPGETTIME, &tv))
  {
    perror ("PPNEGOT");
    close (fd);
    return 1;
  }
  printf("sec %u usec %u\n",tv.tv_sec, tv.tv_usec);
  tv.tv_sec = 50;
  tv.tv_usec = 1000;
  if (ioctl(fd, PPSETTIME, &tv))
  {
    perror ("PPNEGOT");
    close (fd);
    return 1;
  }
  if (ioctl(fd, PPGETTIME, &tv))
  {
    perror ("PPNEGOT");
    close (fd);
    return 1;
  }
  printf("sec %u usec %u\n",tv.tv_sec, tv.tv_usec);
  ioctl (fd, PPRELEASE);
  close(fd);
}