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. WARN() and return 0 in such
cases.

Cc: Marco Elver <elver@google.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 500eb777faca664d44ceced39f282af621603794..7972ec4b9ca42c62d2a43ad1f206781f8d5b8e52 100644 (file)
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -984,8 +984,13 @@ size_t __ksize(const void *object)
 
        folio = virt_to_folio(object);
 
-       if (unlikely(!folio_test_slab(folio)))
+       if (unlikely(!folio_test_slab(folio))) {
+               if (WARN_ON(folio_size(folio) <= KMALLOC_MAX_CACHE_SIZE))
+                       return 0;
+               if (WARN_ON(object != folio_address(folio)))
+                       return 0;
                return folio_size(folio);
+       }
 
        return slab_ksize(folio_slab(folio)->slab_cache);
 }