On Tue, Feb 15, 2022 at 10:18:15AM +0100, Arnd Bergmann wrote:

On Mon, Feb 14, 2022 at 6:01 PM Christoph Hellwig [off-list ref] wrote:

quoted

On Mon, Feb 14, 2022 at 05:34:41PM +0100, Arnd Bergmann wrote:

quoted

From: Arnd Bergmann <arnd@arndb.de>

The get_user()/put_user() functions are meant to check for
access_ok(), while the __get_user()/__put_user() functions
don't.

This broke in 4.19 for nds32, when it gained an extraneous
check in __get_user(), but lost the check it needs in
__put_user().

Can we follow the lead of MIPS (which this was originally copied
from I think) and kill the pointless __get/put_user_check wrapper
that just obsfucate the code?

I had another look, but I think that would be a bigger change than
I want to have in a fix for stable backports, as nds32 also uses
the _check versions in __{get,put}_user_error.

Don't worry about stable backports first, get it correct and merged and
then worry about them if you really have to.

If someone cares about nds32 for stable kernels, they can do the
backport work :)

thanks,

greg k-h