linux-kernel - [PATCH 16/20] kasan: simplify assign_tag and set

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Message-Id: <d4149b16fe2fd29e57a0bb8d997354676f76a183.1604534322.git.andreyknvl@google.com>
Date:   Thu,  5 Nov 2020 01:02:26 +0100
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>,
        Andrey Ryabinin <aryabinin@...tuozzo.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 16/20] kasan: simplify assign_tag and set_tag calls

set_tag() already ignores the tag for the generic mode, so just call it
as is. Add a check for the generic mode to assign_tag(), and simplify its
call in ____kasan_kmalloc().

Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>
Link: https://linux-review.googlesource.com/id/I18905ca78fb4a3d60e1a34a4ca00247272480438
---
 mm/kasan/common.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 69ab880abacc..40ff3ce07a76 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -238,6 +238,9 @@ void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
 static u8 assign_tag(struct kmem_cache *cache, const void *object,
 			bool init, bool keep_tag)
 {
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		return 0xff;
+
 	/*
 	 * 1. When an object is kmalloc()'ed, two hooks are called:
 	 *    kasan_slab_alloc() and kasan_kmalloc(). We assign the
@@ -280,8 +283,8 @@ void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
 		__memset(alloc_meta, 0, sizeof(*alloc_meta));
 	}
 
-	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) || IS_ENABLED(CONFIG_KASAN_HW_TAGS))
-		object = set_tag(object, assign_tag(cache, object, true, false));
+	/* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */
+	object = set_tag(object, assign_tag(cache, object, true, false));
 
 	return (void *)object;
 }
@@ -362,9 +365,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object,
 				KASAN_GRANULE_SIZE);
 	redzone_end = round_up((unsigned long)object + cache->object_size,
 				KASAN_GRANULE_SIZE);
-
-	if (IS_ENABLED(CONFIG_KASAN_SW_TAGS) || IS_ENABLED(CONFIG_KASAN_HW_TAGS))
-		tag = assign_tag(cache, object, false, keep_tag);
+	tag = assign_tag(cache, object, false, keep_tag);
 
 	/* Tag is ignored in set_tag without CONFIG_KASAN_SW/HW_TAGS */
 	kasan_unpoison_memory(set_tag(object, tag), size);
-- 
2.29.1.341.ge80a0c044ae-goog