[SCSI] compat_ioct: fix bsg SG_IO

bsg's SG_IO doesn't work on 32-bit userspace and 64-bit kernelspace.

The problem is that both sg and bsg drivers use SG_IO
ioctl. sg_ioctl_trans() does 32/64-bit conversion even against bsg
header. It messes up bsg header. bsg driver gets garbage.

This patch fixes sg_ioctl_trans to handle only sg header (struct
sg_io_hdr).

Reported-by: Giridhar Malavali <[e-mail]>
Signed-off-by: FUJITA Tomonori <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

fs/compat_ioctl.c

···
 	u32 data;
 	void __user *dxferp;
 	int err;
+	int interface_id;
+
+	if (get_user(interface_id, &sgio32->interface_id))
+		return -EFAULT;
+	if (interface_id != 'S')
+		return sys_ioctl(fd, cmd, (unsigned long)sgio32);
 
 	if (get_user(iovec_count, &sgio32->iovec_count))
 		return -EFAULT;