From 0b3eb091d5759479d44cb793fad2c51ea06bdcec Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Mon, 4 Oct 2021 14:45:56 +0100 Subject: [PATCH] mm: Convert check_heap_object() to use struct slab Ensure that we're not seeing a tail page inside __check_heap_object() by converting to a slab instead of a page. Take the opportunity to mark the slab as const since we're not modifying it. Also move the declaration of __check_heap_object() to mm/slab.h so it's not available to the wider kernel. [ vbabka@suse.cz: in check_heap_object() only convert to struct slab for actual PageSlab pages; use folio as intermediate step instead of page ] Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Vlastimil Babka Reviewed-by: Roman Gushchin --- include/linux/slab.h | 8 -------- mm/slab.c | 14 +++++++------- mm/slab.h | 11 +++++++++++ mm/slub.c | 10 +++++----- mm/usercopy.c | 13 +++++++------ 5 files changed, 30 insertions(+), 26 deletions(-) diff --git a/include/linux/slab.h b/include/linux/slab.h index 181045148b06..367366f1d1ff 100644 --- a/include/linux/slab.h +++ b/include/linux/slab.h @@ -189,14 +189,6 @@ bool kmem_valid_obj(void *object); void kmem_dump_obj(void *object); #endif -#ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR -void __check_heap_object(const void *ptr, unsigned long n, struct page *page, - bool to_user); -#else -static inline void __check_heap_object(const void *ptr, unsigned long n, - struct page *page, bool to_user) { } -#endif - /* * Some archs want to perform DMA into kmalloc caches and need a guaranteed * alignment larger than the alignment of a 64-bit integer. diff --git a/mm/slab.c b/mm/slab.c index 44bc1fcd1393..38fcd3f496df 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -372,8 +372,8 @@ static void **dbg_userword(struct kmem_cache *cachep, void *objp) static int slab_max_order = SLAB_MAX_ORDER_LO; static bool slab_max_order_set __initdata; -static inline void *index_to_obj(struct kmem_cache *cache, struct page *page, - unsigned int idx) +static inline void *index_to_obj(struct kmem_cache *cache, + const struct page *page, unsigned int idx) { return page->s_mem + cache->size * idx; } @@ -4166,8 +4166,8 @@ ssize_t slabinfo_write(struct file *file, const char __user *buffer, * Returns NULL if check passes, otherwise const char * to name of cache * to indicate an error. */ -void __check_heap_object(const void *ptr, unsigned long n, struct page *page, - bool to_user) +void __check_heap_object(const void *ptr, unsigned long n, + const struct slab *slab, bool to_user) { struct kmem_cache *cachep; unsigned int objnr; @@ -4176,15 +4176,15 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page, ptr = kasan_reset_tag(ptr); /* Find and validate object. */ - cachep = page->slab_cache; - objnr = obj_to_index(cachep, page, (void *)ptr); + cachep = slab->slab_cache; + objnr = obj_to_index(cachep, slab_page(slab), (void *)ptr); BUG_ON(objnr >= cachep->num); /* Find offset within object. */ if (is_kfence_address(ptr)) offset = ptr - kfence_object_start(ptr); else - offset = ptr - index_to_obj(cachep, page, objnr) - obj_offset(cachep); + offset = ptr - index_to_obj(cachep, slab_page(slab), objnr) - obj_offset(cachep); /* Allow address range falling entirely within usercopy region. */ if (offset >= cachep->useroffset && diff --git a/mm/slab.h b/mm/slab.h index 9ae9f6c3d1cb..039babfde2fe 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -812,4 +812,15 @@ struct kmem_obj_info { void kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab); #endif +#ifdef CONFIG_HAVE_HARDENED_USERCOPY_ALLOCATOR +void __check_heap_object(const void *ptr, unsigned long n, + const struct slab *slab, bool to_user); +#else +static inline +void __check_heap_object(const void *ptr, unsigned long n, + const struct slab *slab, bool to_user) +{ +} +#endif + #endif /* MM_SLAB_H */ diff --git a/mm/slub.c b/mm/slub.c index 8e9667815f81..8b82188849ae 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4485,8 +4485,8 @@ EXPORT_SYMBOL(__kmalloc_node); * Returns NULL if check passes, otherwise const char * to name of cache * to indicate an error. */ -void __check_heap_object(const void *ptr, unsigned long n, struct page *page, - bool to_user) +void __check_heap_object(const void *ptr, unsigned long n, + const struct slab *slab, bool to_user) { struct kmem_cache *s; unsigned int offset; @@ -4495,10 +4495,10 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page, ptr = kasan_reset_tag(ptr); /* Find object and usable object size. */ - s = page->slab_cache; + s = slab->slab_cache; /* Reject impossible pointers. */ - if (ptr < page_address(page)) + if (ptr < slab_address(slab)) usercopy_abort("SLUB object not in SLUB page?!", NULL, to_user, 0, n); @@ -4506,7 +4506,7 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page, if (is_kfence) offset = ptr - kfence_object_start(ptr); else - offset = (ptr - page_address(page)) % s->size; + offset = (ptr - slab_address(slab)) % s->size; /* Adjust for redzone and reject if within the redzone. */ if (!is_kfence && kmem_cache_debug_flags(s, SLAB_RED_ZONE)) { diff --git a/mm/usercopy.c b/mm/usercopy.c index b3de3c4eefba..d0d268135d96 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -20,6 +20,7 @@ #include #include #include +#include "slab.h" /* * Checks if a given pointer and length is contained by the current @@ -223,7 +224,7 @@ static inline void check_page_span(const void *ptr, unsigned long n, static inline void check_heap_object(const void *ptr, unsigned long n, bool to_user) { - struct page *page; + struct folio *folio; if (!virt_addr_valid(ptr)) return; @@ -231,16 +232,16 @@ static inline void check_heap_object(const void *ptr, unsigned long n, /* * When CONFIG_HIGHMEM=y, kmap_to_page() will give either the * highmem page or fallback to virt_to_page(). The following - * is effectively a highmem-aware virt_to_head_page(). + * is effectively a highmem-aware virt_to_slab(). */ - page = compound_head(kmap_to_page((void *)ptr)); + folio = page_folio(kmap_to_page((void *)ptr)); - if (PageSlab(page)) { + if (folio_test_slab(folio)) { /* Check slab allocator for flags and size. */ - __check_heap_object(ptr, n, page, to_user); + __check_heap_object(ptr, n, folio_slab(folio), to_user); } else { /* Verify object does not incorrectly span multiple pages. */ - check_page_span(ptr, n, page, to_user); + check_page_span(ptr, n, folio_page(folio, 0), to_user); } } -- 2.11.0