Commit 70c248ac authored by Catalin Marinas's avatar Catalin Marinas Committed by Will Deacon
Browse files

mm: kasan: Skip unpoisoning of user pages 



Commit c275c5c6 ("kasan: disable freed user page poisoning with HW
tags") added __GFP_SKIP_KASAN_POISON to GFP_HIGHUSER_MOVABLE. A similar
argument can be made about unpoisoning, so also add
__GFP_SKIP_KASAN_UNPOISON to user pages. To ensure the user page is
still accessible via page_address() without a kasan fault, reset the
page->flags tag.

With the above changes, there is no need for the arm64
tag_clear_highpage() to reset the page->flags tag.

Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: default avatarVincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: default avatarAndrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20220610152141.2148929-3-catalin.marinas@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent ed0a6d1d

arch/arm64/mm/fault.c

+0 −1
Original line number Diff line number Diff line
@@ -927,6 +927,5 @@ struct page *alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma, 
void tag_clear_highpage(struct page *page)

{

	mte_zero_clear_page_tags(page_address(page));

	page_kasan_tag_reset(page);

	set_bit(PG_mte_tagged, &page->flags);

}

include/linux/gfp.h

+1 −1
Original line number Diff line number Diff line
@@ -348,7 +348,7 @@ struct vm_area_struct; 
#define GFP_DMA32	__GFP_DMA32

#define GFP_HIGHUSER	(GFP_USER | __GFP_HIGHMEM)

#define GFP_HIGHUSER_MOVABLE	(GFP_HIGHUSER | __GFP_MOVABLE | \

			 __GFP_SKIP_KASAN_POISON)

			 __GFP_SKIP_KASAN_POISON | __GFP_SKIP_KASAN_UNPOISON)

#define GFP_TRANSHUGE_LIGHT	((GFP_HIGHUSER_MOVABLE | __GFP_COMP | \

			 __GFP_NOMEMALLOC | __GFP_NOWARN) & ~__GFP_RECLAIM)

#define GFP_TRANSHUGE	(GFP_TRANSHUGE_LIGHT | __GFP_DIRECT_RECLAIM)

mm/page_alloc.c

+5 −2
Original line number Diff line number Diff line
@@ -2397,6 +2397,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order, 
	bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags) &&

			!should_skip_init(gfp_flags);

	bool init_tags = init && (gfp_flags & __GFP_ZEROTAGS);

	int i;



	set_page_private(page, 0);

	set_page_refcounted(page);
@@ -2422,8 +2423,6 @@ inline void post_alloc_hook(struct page *page, unsigned int order, 
	 * should be initialized as well).

	 */

	if (init_tags) {

		int i;



		/* Initialize both memory and tags. */

		for (i = 0; i != 1 << order; ++i)

			tag_clear_highpage(page + i);
@@ -2438,6 +2437,10 @@ inline void post_alloc_hook(struct page *page, unsigned int order, 
		/* Note that memory is already initialized by KASAN. */

		if (kasan_has_integrated_init())

			init = false;

	} else {

		/* Ensure page_address() dereferencing does not fault. */

		for (i = 0; i != 1 << order; ++i)

			page_kasan_tag_reset(page + i);

	}

	/* If memory is still not initialized, do it now. */

	if (init)