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

Robin Murphy
2020-10-27T17:35:24Z

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>

> 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);
>