linux-kernel - [PATCH v6 14/39] kasan, page_alloc: rework kasan_unpoison

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Date:   Mon, 24 Jan 2022 19:02:22 +0100
From:   andrey.konovalov@...ux.dev
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH v6 14/39] kasan, page_alloc: rework kasan_unpoison_pages call site

From: Andrey Konovalov <andreyknvl@...gle.com>

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@...gle.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 2784bd478942..3af38e323391 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2434,15 +2434,20 @@ 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