linux-kernel - [PATCH v3 1/3] mm/slub: Consider kfence case for get_orig

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Message-Id: <20241016154152.1376492-2-feng.tang@intel.com>
Date: Wed, 16 Oct 2024 23:41:50 +0800
From: Feng Tang <feng.tang@...el.com>
To: Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Marco Elver <elver@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Narasimhan.V@....com
Cc: linux-mm@...ck.org,
	kasan-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	Feng Tang <feng.tang@...el.com>
Subject: [PATCH v3 1/3] mm/slub: Consider kfence case for get_orig_size()

When 'orig_size' of kmalloc object is enabled by debug option, it
should either contains the actual requested size or the cache's
'object_size'.

But it's not true if that object is a kfence-allocated one, and the
data at 'orig_size' offset of metadata could be zero or other values.
This is not a big issue for current 'orig_size' usage, as init_object()
and check_object() during alloc/free process will be skipped for kfence
addresses. But it could cause trouble for other usage in future.

Use the existing kfence helper kfence_ksize() which can return the
real original request size.

Signed-off-by: Feng Tang <feng.tang@...el.com>
---
 mm/slub.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/slub.c b/mm/slub.c
index af9a80071fe0..1d348899f7a3 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -768,6 +768,9 @@ static inline unsigned int get_orig_size(struct kmem_cache *s, void *object)
 {
 	void *p = kasan_reset_tag(object);

+	if (is_kfence_address(object))
+		return kfence_ksize(object);
+
 	if (!slub_debug_orig_size(s))
 		return s->object_size;

-- 
2.27.0