On 02/15/2017 12:20 PM, Cyril Hrubis wrote:
> The BLKRASET/BLKRAGET ioctls() take unsigned long, if I pass int * to
> the BLKRAGET ioctl on x86_64 (or on any other arch where sizeof(int) !=
> sizeof(long)) the BLKRAGET ioctl will rewrite four bytes on the stack.
>
> If you look at block/ioctl.c in kernel sources you can clearly see that
> BLKRAGET ioctl calls put_long().
>
> Compile following reproducer and run it as ./a.out /dev/sda, you can see
> that the second member of the array will be zeroed. If you change the
> array to have only one member you will see stack smashing trace.
>
> I also wonder if it's OK to pass int value to ioctl() at all, the arg
> value seems to be unsigned long in the syscall definition in fs/ioctl.c
> and there does not seem to be any glibc magic around the syscall.
Thanks Cyril. Applied now. Sorry for the delayed response...
Cheers,
Michael
> -------------------------8<----------------------------
> #include <sys/mount.h>
> #include <sys/ioctl.h>
> #include <fcntl.h>
> #include <stdio.h>
>
> static int fd;
>
> int main(int argc, char *argv[])
> {
> int ra[] = {100, 100};
>
> fd = open(argv[1], O_RDONLY);
> if (fd < 0) {
> perror("open");
> return 1;
> }
>
> ioctl(fd, BLKRAGET, ra);
>
> fprintf(stderr, "%i %i\n", ra[0], ra[1]);
>
> return 0;
> }
>
> -------------------------8<----------------------------
>
> Signed-off-by: Cyril Hrubis <chrubis@xxxxxxx>
> ---
> man2/ioctl_list.2 | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/man2/ioctl_list.2 b/man2/ioctl_list.2
> index 0165c77..c8efd66 100644
> --- a/man2/ioctl_list.2
> +++ b/man2/ioctl_list.2
> @@ -311,8 +311,8 @@ l l l l.
> 0x0000125F BLKRRPART void
> 0x00001260 BLKGETSIZE unsigned long *
> 0x00001261 BLKFLSBUF void
> -0x00001262 BLKRASET int
> -0x00001263 BLKRAGET int *
> +0x00001262 BLKRASET unsigned long
> +0x00001263 BLKRAGET unsigned long *
> 0x00000001 FIBMAP int * // I-O
> 0x00000002 FIGETBSZ int *
> 0x80086601 FS_IOC_GETFLAGS int *
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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