diff mbox series

[mm,v10,31/42] kasan, mm: untag page address in free_reserved_area

Message ID b167fd21b86e7d728ba3a8e20be4f7e8373bc22c.1605305705.git.andreyknvl@google.com (mailing list archive)
State New
Headers show
Series kasan: add hardware tag-based mode for arm64 | expand

Commit Message

Andrey Konovalov Nov. 13, 2020, 10:15 p.m. UTC
From: Vincenzo Frascino <vincenzo.frascino@arm.com>

free_reserved_area() memsets the pages belonging to a given memory area.
As that memory hasn't been allocated via page_alloc, the KASAN tags that
those pages have are 0x00. As the result the memset might result in a tag
mismatch.

Untag the address to avoid spurious faults.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
Change-Id: If12b4944383575b8bbd7d971decbd7f04be6748b
---
 mm/page_alloc.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Alexander Potapenko Nov. 18, 2020, 4:07 p.m. UTC | #1
On Fri, Nov 13, 2020 at 11:17 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
>
> free_reserved_area() memsets the pages belonging to a given memory area.
> As that memory hasn't been allocated via page_alloc, the KASAN tags that
> those pages have are 0x00. As the result the memset might result in a tag
> mismatch.
>
> Untag the address to avoid spurious faults.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Alexander Potapenko <glider@google.com>

> ---
> Change-Id: If12b4944383575b8bbd7d971decbd7f04be6748b
> ---
>  mm/page_alloc.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 855627e52f81..4a69fef13ac7 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7653,6 +7653,11 @@ unsigned long free_reserved_area(void *start, void *end, int poison, const char
>                  * alias for the memset().
>                  */
>                 direct_map_addr = page_address(page);
> +               /*
> +                * Perform a kasan-unchecked memset() since this memory
> +                * has not been initialized.
> +                */
> +               direct_map_addr = kasan_reset_tag(direct_map_addr);
>                 if ((unsigned int)poison <= 0xFF)
>                         memset(direct_map_addr, poison, PAGE_SIZE);
>
> --
> 2.29.2.299.gdc1121823c-goog
>
diff mbox series

Patch

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 855627e52f81..4a69fef13ac7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7653,6 +7653,11 @@  unsigned long free_reserved_area(void *start, void *end, int poison, const char
 		 * alias for the memset().
 		 */
 		direct_map_addr = page_address(page);
+		/*
+		 * Perform a kasan-unchecked memset() since this memory
+		 * has not been initialized.
+		 */
+		direct_map_addr = kasan_reset_tag(direct_map_addr);
 		if ((unsigned int)poison <= 0xFF)
 			memset(direct_map_addr, poison, PAGE_SIZE);