[PATCH] mm: Add additional consistency check

[Kees Cook]

As found in PaX, this adds a cheap check on heap consistency, just to
notice if things have gotten corrupted in the page lookup.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 mm/slab.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/slab.h b/mm/slab.h
index 65e7c3fcac72..64447640b70c 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -384,6 +384,7 @@ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x)
 		return s;
 
 	page = virt_to_head_page(x);
+	BUG_ON(!PageSlab(page));
 	cachep = page->slab_cache;
 	if (slab_equal_or_root(cachep, s))
 		return cachep;
-- 
2.7.4


-- 
Kees Cook
Pixel Security