Commit c275c5c6d50a ("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@xxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Peter Collingbourne <pcc@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
---
arch/arm64/mm/fault.c | 1 -
include/linux/gfp.h | 2 +-
mm/page_alloc.c | 7 +++++--
3 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index c5e11768e5c1..cdf3ffa0c223 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -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);
}
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 2d2ccae933c2..0ace7759acd2 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -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)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e008a3df0485..f6ed240870bc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -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)
