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mm: kasan: Skip unpoisoning of user pages 

Commit c275c5c6d5 ("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: Catalin 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: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Link: https://lore.kernel.org/r/20220610152141.2148929-3-catalin.marinas@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Catalin Marinas 2022-06-10 16:21:39 +01:00 committed by Will Deacon
parent ed0a6d1d97
commit 70c248aca9
3 changed files with 6 additions and 4 deletions
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1
arch/arm64/mm/fault.c
View File

@ -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);
}

2
include/linux/gfp.h
View File

@ -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)

7
mm/page_alloc.c
View File

@ -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)