On Mon, Jan 07, 2019 at 08:29:38AM -0800, David Miller wrote:

From: Eugene Syromiatnikov <redacted>
Date: Mon, 7 Jan 2019 16:22:29 +0100

quoted

Otherwise it is impossible to use it for something else, as it will break
userspace that puts garbage there.

The same check should be done in other structures, but the fact that
data in reserved fields is ignored is already part of the kernel ABI.

Signed-off-by: Eugene Syromiatnikov <redacted>

I think the opportunity to enforce this has passed and you will break
userspace by doing this.

FWIW, this ioctl wasn't present in a stable Linux release yet and the
two applications that I know that support it both zero the rsv field,
so I think at least this patch is very unlikely to break anything.

Anyway, thanks to Eugene for catching the issues.

-- 
Miroslav Lichvar