From:   andrey.konovalov@linux.dev
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Andrey Konovalov <andreyknvl@gmail.com>,
        Marco Elver <elver@google.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        kasan-dev@googlegroups.com, linux-mm@kvack.org,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        linux-arm-kernel@lists.infradead.org,
        Peter Collingbourne <pcc@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
Subject: [PATCH mm v5 14/39] kasan, page_alloc: rework kasan_unpoison_pages call site
Date:   Thu, 30 Dec 2021 20:12:16 +0100
Message-Id: <ec4ff45bcc6fab1d4780fbf132898ff5541acff1.1640891329.git.andreyknvl@google.com>
In-Reply-To: <cover.1640891329.git.andreyknvl@google.com>
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From: Andrey Konovalov <andreyknvl@google.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@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 ddf677c23298..a07f9e9b0abc 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