linux-kernel - [PATCH mm v3 01/34] kasan: check KASAN_NO_FREE_META in __kasan_metadata

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Date:   Mon,  5 Sep 2022 23:05:16 +0200
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, Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Florian Mayer <fmayer@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: [PATCH mm v3 01/34] kasan: check KASAN_NO_FREE_META in __kasan_metadata_size

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

__kasan_metadata_size() calculates the size of the redzone for objects
in a slab cache.

When accounting for presence of kasan_free_meta in the redzone, this
function only compares free_meta_offset with 0. But free_meta_offset could
also be equal to KASAN_NO_FREE_META, which indicates that kasan_free_meta
is not present at all.

Add a comparison with KASAN_NO_FREE_META into __kasan_metadata_size().

Reviewed-by: Marco Elver <elver@...gle.com>
Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>

---

This is a minor fix that only affects slub_debug runs, so it is probably
not worth backporting.
---
 mm/kasan/common.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 69f583855c8b..f6a6c7d0d8b8 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -224,8 +224,9 @@ size_t __kasan_metadata_size(struct kmem_cache *cache)
 		return 0;
 	return (cache->kasan_info.alloc_meta_offset ?
 		sizeof(struct kasan_alloc_meta) : 0) +
-		(cache->kasan_info.free_meta_offset ?
-		sizeof(struct kasan_free_meta) : 0);
+		((cache->kasan_info.free_meta_offset &&
+		  cache->kasan_info.free_meta_offset != KASAN_NO_FREE_META) ?
+		 sizeof(struct kasan_free_meta) : 0);
 }
 
 struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
-- 
2.25.1