linux-kernel - [PATCH v4 17/17] mm/sl[au]b: check if large object is valid in _

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Date:   Wed, 17 Aug 2022 19:18:26 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Marco Elver <elver@...gle.com>
Subject: [PATCH v4 17/17] mm/sl[au]b: check if large object is valid in __ksize()

If address of large object is not beginning of folio or size of
the folio is too small, it must be invalid. BUG() in such cases.

Cc: Marco Elver <elver@...gle.com>
Suggested-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
Reviewed-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slab_common.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 9c273a5fb0d7..98d029212682 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -984,8 +984,11 @@ size_t __ksize(const void *object)
 
 	folio = virt_to_folio(object);
 
-	if (unlikely(!folio_test_slab(folio)))
+	if (unlikely(!folio_test_slab(folio))) {
+		BUG_ON(folio_size(folio) <= KMALLOC_MAX_CACHE_SIZE);
+		BUG_ON(object != folio_address(folio));
 		return folio_size(folio);
+	}
 
 	return slab_ksize(folio_slab(folio)->slab_cache);
 }
-- 
2.32.0