Re: [3/7,media] dvb: don't use 'time_t' in event ioctl

On Wed, Aug 30, 2017 at 10:25:01PM +0200, Arnd Bergmann wrote:

quoted

quoted

diff --git a/include/uapi/linux/dvb/video.h b/include/uapi/linux/dvb/video.h
index d3d14a59d2d5..6c7f9298d7c2 100644
--- a/include/uapi/linux/dvb/video.h
+++ b/include/uapi/linux/dvb/video.h

@@ -135,7 +135,8 @@ struct video_event {
 #define VIDEO_EVENT_FRAME_RATE_CHANGED       2
 #define VIDEO_EVENT_DECODER_STOPPED  3
 #define VIDEO_EVENT_VSYNC            4
-     __kernel_time_t timestamp;
+     /* unused, make sure to use atomic time for y2038 if it ever gets used */
+     long timestamp;

This change breaks x32 ABI (and possibly MIPS n32 ABI), as __kernel_time_t
there is 64 bit already:
https://sourceforge.net/p/strace/mailman/message/36015326/

Note the change in structure size from 0x20 to 0x14 for VIDEO_GET_EVENT
command in linux/x32/ioctls_inc0.h.

Are you sure it worked before the change? I don't see any handler in the kernel
for the x32 compat ioctl call here, only the compat_video_event handling, so
my guess is that the change unintentionally fixes x32.

Yes, you're right; unfortunately, I decided to check which ioctl handler
x32 code is using only after sending the e-mail, and now in the process
of preparing some RFC patch for the ioctl commands which have discrepancies
between x32 and compat sizes.

         Arnd