From a64b53780ec35b77daf817210c88aa42d172c98f Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 11 Jul 2019 20:53:26 -0700 Subject: mm/slab: sanity-check page type when looking up cache This avoids any possible type confusion when looking up an object. For example, if a non-slab were to be passed to kfree(), the invalid slab_cache pointer (i.e. overlapped with some other value from the struct page union) would be used for subsequent slab manipulations that could lead to further memory corruption. Since the page is already in cache, adding the PageSlab() check will have nearly zero cost, so add a check and WARN() to virt_to_cache(). Additionally replaces an open-coded virt_to_cache(). To support the failure mode this also updates all callers of virt_to_cache() and cache_from_obj() to handle a NULL cache pointer return value (though note that several already handle this case gracefully). [dan.carpenter@oracle.com: restore IRQs in kfree()] Link: http://lkml.kernel.org/r/20190613065637.GE16334@mwanda Link: http://lkml.kernel.org/r/20190530045017.15252-3-keescook@chromium.org Signed-off-by: Kees Cook Signed-off-by: Dan Carpenter Cc: Alexander Popov Cc: Alexander Potapenko Cc: Christoph Lameter Cc: David Rientjes Cc: Greg Kroah-Hartman Cc: Joonsoo Kim Cc: Matthew Wilcox Cc: Pekka Enberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slab.h | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) (limited to 'mm/slab.h') diff --git a/mm/slab.h b/mm/slab.h index 4dafae2c8620..739099af6cbb 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -350,10 +350,20 @@ static inline void memcg_link_cache(struct kmem_cache *s) #endif /* CONFIG_MEMCG_KMEM */ +static inline struct kmem_cache *virt_to_cache(const void *obj) +{ + struct page *page; + + page = virt_to_head_page(obj); + if (WARN_ONCE(!PageSlab(page), "%s: Object is not a Slab page!\n", + __func__)) + return NULL; + return page->slab_cache; +} + static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x) { struct kmem_cache *cachep; - struct page *page; /* * When kmemcg is not being used, both assignments should return the @@ -367,9 +377,8 @@ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x) !unlikely(s->flags & SLAB_CONSISTENCY_CHECKS)) return s; - page = virt_to_head_page(x); - cachep = page->slab_cache; - WARN_ONCE(!slab_equal_or_root(cachep, s), + cachep = virt_to_cache(x); + WARN_ONCE(cachep && !slab_equal_or_root(cachep, s), "%s: Wrong slab cache. %s but object is from %s\n", __func__, s->name, cachep->name); return cachep; -- cgit v1.2.3