[PATCH mm v4 14/39] kasan, page_alloc: rework kasan_unpoison_pages call site

andrey.konovalov
2021-12-20T22:00:12Z

Rework the checks around kasan_unpoison_pages() call in
post_alloc_hook().

The logical condition for calling this function is:

- If a software KASAN mode is enabled, we need to mark shadow memory.
- Otherwise, HW_TAGS KASAN is enabled, and it only makes sense to
set tags if they haven't already been cleared by tag_clear_highpage(),
which is indicated by init_tags.

This patch concludes the changes for post_alloc_hook().

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

---

Changes v3->v4:
- Make the confition checks more explicit.
- Update patch description.
---
mm/page_alloc.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 205884e3520b..2ef0f531e881 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2433,15 +2433,20 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
/* Note that memory is already initialized by the loop above. */
init = false;
}
- if (kasan_has_integrated_init()) {
- if (!init_tags) {
- kasan_unpoison_pages(page, order, init);
+ /*
+ * If either a software KASAN mode is enabled, or,
+ * in the case of hardware tag-based KASAN,
+ * if memory tags have not been cleared via tag_clear_highpage().
+ */
+ if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
+ IS_ENABLED(CONFIG_KASAN_SW_TAGS) ||
+ kasan_hw_tags_enabled() && !init_tags) {
+ /* Mark shadow memory or set memory tags. */
+ kasan_unpoison_pages(page, order, init);

- /* Note that memory is already initialized by KASAN. */
+ /* Note that memory is already initialized by KASAN. */
+ if (kasan_has_integrated_init())
init = false;
- }
- } else {
- kasan_unpoison_pages(page, order, init);
}
/* If memory is still not initialized, do it now. */
if (init)
--
2.25.1