Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the SLAB allocator to catch any copies that may span objects. Based on code from PaX and grsecurity. Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- init/Kconfig | 1 + mm/slab.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index f755a602d4a1..798c2020ee7c 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1757,6 +1757,7 @@ choice config SLAB bool "SLAB" + select HAVE_HARDENED_USERCOPY_ALLOCATOR help The regular slab allocator that is established and known to work well in all environments. It organizes cache hot objects in diff --git a/mm/slab.c b/mm/slab.c index cc8bbc1e6bc9..5e2d5f349aca 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -4477,6 +4477,36 @@ static int __init slab_proc_init(void) module_init(slab_proc_init); #endif +#ifdef CONFIG_HARDENED_USERCOPY +/* + * Rejects objects that are incorrectly sized. + * + * Returns NULL if check passes, otherwise const char * to name of cache + * to indicate an error. + */ +const char *__check_heap_object(const void *ptr, unsigned long n, + struct page *page) +{ + struct kmem_cache *cachep; + unsigned int objnr; + unsigned long offset; + + /* Find and validate object. */ + cachep = page->slab_cache; + objnr = obj_to_index(cachep, page, (void *)ptr); + BUG_ON(objnr >= cachep->num); + + /* Find offset within object. */ + offset = ptr - index_to_obj(cachep, page, objnr) - obj_offset(cachep); + + /* Allow address range falling entirely within object size. */ + if (offset <= cachep->object_size && n <= cachep->object_size - offset) + return NULL; + + return cachep->name; +} +#endif /* CONFIG_HARDENED_USERCOPY */ + /** * ksize - get the actual amount of memory allocated for a given object * @objp: Pointer to the object -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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