Re: [PATCH 03/14] nds32: fix access_ok() checks in get/put_user
On Tue, Feb 15, 2022 at 10:18:15AM +0100, Arnd Bergmann wrote:
> On Mon, Feb 14, 2022 at 6:01 PM Christoph Hellwig wrote:
> >
> > On Mon, Feb 14, 2022 at 05:34:41PM +0100, Arnd Bergmann wrote:
> > > From: Arnd Bergmann
> > >
> > > 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
Re: [PATCH 03/14] nds32: fix access_ok() checks in get/put_user
On Mon, Feb 14, 2022 at 6:01 PM Christoph Hellwig wrote:
>
> On Mon, Feb 14, 2022 at 05:34:41PM +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann
> >
> > 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.
If we instead clean it up in a separate patch, it should be done for
all eight architectures that do the same thing, but at that point,
the time seems better spent at coming up with a new set of
calling conventions that work with asm-goto.
Arnd
RE: [PATCH 03/14] nds32: fix access_ok() checks in get/put_user
From: Christoph Hellwig > Sent: 14 February 2022 17:01 > > On Mon, Feb 14, 2022 at 05:34:41PM +0100, Arnd Bergmann wrote: > > From: Arnd Bergmann > > > > 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? Is it possible to make all these architectures fall back to a common definition somewhere? Maybe they need to define ACCESS_OK_USER_LIMIT - which can be different from TASK_SIZE. There'll be a few special cases, but most architectures have kernel addresses above userspace ones. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
Re: [PATCH 03/14] nds32: fix access_ok() checks in get/put_user
On Mon, Feb 14, 2022 at 05:34:41PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann > > 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?
