Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Sender: "andreyknvl via sendgmr" <andreyknvl@andreyknvl3.muc.corp.google.com>
Date:   Fri,  5 Feb 2021 16:39:04 +0100
In-Reply-To: <cover.1612538932.git.andreyknvl@google.com>
Message-Id: <97581e50e594596e0bf8dd5bb3598d5e13013f18.1612538932.git.andreyknvl@google.com>
Mime-Version: 1.0
References: <cover.1612538932.git.andreyknvl@google.com>
Subject: [PATCH v2 03/12] kasan: optimize large kmalloc poisoning
From:   Andrey Konovalov <andreyknvl@google.com>
To:     Andrew Morton <akpm@linux-foundation.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>
Cc:     Will Deacon <will.deacon@arm.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Peter Collingbourne <pcc@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Similarly to kasan_kmalloc(), kasan_kmalloc_large() doesn't need
to unpoison the object as it as already unpoisoned by alloc_pages()
(or by ksize() for krealloc()).

This patch changes kasan_kmalloc_large() to only poison the redzone.

Reviewed-by: Marco Elver <elver@google.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/kasan/common.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 00edbc3eb32e..f2a6bae13053 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -494,7 +494,6 @@ EXPORT_SYMBOL(__kasan_kmalloc);
 void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
 						gfp_t flags)
 {
-	struct page *page;
 	unsigned long redzone_start;
 	unsigned long redzone_end;
 
@@ -504,12 +503,23 @@ void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
 	if (unlikely(ptr == NULL))
 		return NULL;
 
-	page = virt_to_page(ptr);
+	/*
+	 * The object has already been unpoisoned by kasan_alloc_pages() for
+	 * alloc_pages() or by ksize() for krealloc().
+	 */
+
+	/*
+	 * The redzone has byte-level precision for the generic mode.
+	 * Partially poison the last object granule to cover the unaligned
+	 * part of the redzone.
+	 */
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		kasan_poison_last_granule(ptr, size);
+
+	/* Poison the aligned part of the redzone. */
 	redzone_start = round_up((unsigned long)(ptr + size),
 				KASAN_GRANULE_SIZE);
-	redzone_end = (unsigned long)ptr + page_size(page);
-
-	kasan_unpoison(ptr, size);
+	redzone_end = (unsigned long)ptr + page_size(virt_to_page(ptr));
 	kasan_poison((void *)redzone_start, redzone_end - redzone_start,
 		     KASAN_PAGE_REDZONE);
 
-- 
2.30.0.365.g02bc693789-goog