Re: [RFC PATCH 13/16] arm64: mm: Reset pkey in __tlb_remove_table()

Peter Zijlstra
2024-12-09T10:29:19Z

On Fri, Dec 06, 2024 at 10:11:07AM +0000, Kevin Brodsky wrote:
> Page table pages are typically freed via tlb_remove_table() and
> friends. Ensure that the linear mapping for those pages is reset to
> the default pkey when CONFIG_KPKEYS_HARDENED_PGTABLES is enabled.
>
> This patch is a no-op if CONFIG_KPKEYS_HARDENED_PGTABLES is disabled
> (default).
>
> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
> ---
> arch/arm64/include/asm/tlb.h | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
> index a947c6e784ed..d1611ffa6d91 100644
> --- a/arch/arm64/include/asm/tlb.h
> +++ b/arch/arm64/include/asm/tlb.h
> @@ -10,10 +10,14 @@
>
> #include <linux/pagemap.h>
> #include <linux/swap.h>
> +#include <linux/kpkeys.h>
>
> static inline void __tlb_remove_table(void *_table)
> {
> - free_page_and_swap_cache((struct page *)_table);
> + struct page *page = (struct page *)_table;
> +
> + kpkeys_unprotect_pgtable_memory((unsigned long)page_address(page), 1);
> + free_page_and_swap_cache(page);
> }

Same as for the others, perhaps stick this in generic code instead of in
the arch code?