diff options
| author | Kees Cook <keescook@chromium.org> | 2016-06-23 15:20:59 -0700 |
|---|---|---|
| committer | Kees Cook <keescook@chromium.org> | 2016-07-26 14:41:53 -0700 |
| commit | 04385fc5e8fffed84425d909a783c0f0c587d847 (patch) | |
| tree | 07f94a9ec860dc0bcb6efd2f44632d0a5da29237 | |
| parent | 97433ea4fda62349bfa42089455593cbcb57e06c (diff) | |
mm: SLAB hardened usercopy support
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@chromium.org>
Tested-by: Valdis Kletnieks <valdis.kletnieks@vt.edu>
| -rw-r--r-- | init/Kconfig | 1 | ||||
| -rw-r--r-- | mm/slab.c | 30 |
2 files changed, 31 insertions, 0 deletions
diff --git a/init/Kconfig b/init/Kconfig index c02d89777713..1312d7b5a5fb 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1758,6 +1758,7 @@ 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 |