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mm: SLAB hardened usercopy support

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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>
This commit is contained in:
Kees Cook 2016-06-23 15:20:59 -07:00
parent 97433ea4fd
commit 04385fc5e8
2 changed files with 31 additions and 0 deletions
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1
init/Kconfig
View File

@ -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

30
mm/slab.c
View File

@ -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