Re: [PATCHv3 10/17] arm64: uaccess: simplify __copy_user_flushcache()

Mark Rutland
2020-11-02T10:15:44Z

On Tue, Oct 27, 2020 at 05:33:31PM +0000, Robin Murphy wrote:
> On 2020-10-26 13:31, Mark Rutland wrote:
> > Currently __copy_user_flushcache() open-codes raw_copy_from_user(), and
> > doesn't use uaccess_mask_ptr() on the user address. Let's have it call
> > raw_copy_from_user(), which is both a simplification and ensures that
> > user pointers are masked under speculation.
>
> I think this originally stems from the fact that "raw_*" were merely generic
> aliases for "__arch_*" at the time. Then whichever chump subsequently
> implemented uaccess_mask_ptr() for arm64 clearly did a terrible job... ;)

:)

> > There should be no functional change as a result of this patch.
>
> Reviewed-by: Robin Murphy <robin.murphy@arm.com>

Thanks!

Mark.

>
> > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Robin Murphy <robin.murphy@arm.com>
> > Cc: Will Deacon <will@kernel.org>
> > ---
> > arch/arm64/lib/uaccess_flushcache.c | 4 +---
> > 1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/arch/arm64/lib/uaccess_flushcache.c b/arch/arm64/lib/uaccess_flushcache.c
> > index bfa30b75b2b8e..c83bb5a4aad2c 100644
> > --- a/arch/arm64/lib/uaccess_flushcache.c
> > +++ b/arch/arm64/lib/uaccess_flushcache.c
> > @@ -30,9 +30,7 @@ unsigned long __copy_user_flushcache(void *to, const void __user *from,
> > {
> > unsigned long rc;
> > - uaccess_enable_not_uao();
> > - rc = __arch_copy_from_user(to, from, n);
> > - uaccess_disable_not_uao();
> > + rc = raw_copy_from_user(to, from, n);
> > /* See above */
> > __clean_dcache_area_pop(to, n - rc);
> >