linux-kernel - [PATCH RFC v2 19/21] kasan: don't round

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Date:   Thu, 22 Oct 2020 15:19:11 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>
Cc:     Evgenii Stepanov <eugenis@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Serban Constantinescu <serbanc@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH RFC v2 19/21] kasan: don't round_up too much

For tag-based mode kasan_poison_memory() already rounds up the size. Do
the same for software modes and remove round_up() from common code.

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
Link: https://linux-review.googlesource.com/id/Ib397128fac6eba874008662b4964d65352db4aa4
---
 mm/kasan/common.c | 8 ++------
 mm/kasan/shadow.c | 1 +
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 5622b0ec0907..983383ebe32a 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -215,9 +215,7 @@ void __kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
 
 void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
 {
-	kasan_poison_memory(object,
-			round_up(cache->object_size, KASAN_GRANULE_SIZE),
-			KASAN_KMALLOC_REDZONE);
+	kasan_poison_memory(object, cache->object_size, KASAN_KMALLOC_REDZONE);
 }
 
 /*
@@ -290,7 +288,6 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
 {
 	u8 tag;
 	void *tagged_object;
-	unsigned long rounded_up_size;
 
 	tag = get_tag(object);
 	tagged_object = object;
@@ -311,8 +308,7 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
 		return true;
 	}
 
-	rounded_up_size = round_up(cache->object_size, KASAN_GRANULE_SIZE);
-	kasan_poison_memory(object, rounded_up_size, KASAN_KMALLOC_FREE);
+	kasan_poison_memory(object, cache->object_size, KASAN_KMALLOC_FREE);
 
 	if (static_branch_unlikely(&kasan_stack)) {
 		if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine) ||
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 616ac64c4a21..ab1d39c566b9 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -82,6 +82,7 @@ void kasan_poison_memory(const void *address, size_t size, u8 value)
 	 * addresses to this function.
 	 */
 	address = reset_tag(address);
+	size = round_up(size, KASAN_GRANULE_SIZE);
 
 	shadow_start = kasan_mem_to_shadow(address);
 	shadow_end = kasan_mem_to_shadow(address + size);
-- 
2.29.0.rc1.297.gfa9743e501-goog