diff options
| author | Alexander Potapenko | 2019-10-14 14:11:57 -0700 |
|---|---|---|
| committer | Linus Torvalds | 2019-10-14 15:04:01 -0700 |
| commit | 0f181f9fbea8bc7ea2f7e13ae7f8c256b39e254c (patch) | |
| tree | a6d1d1a674b791224d2430bae6d2fa69f10037b0 | |
| parent | 3c52b0af059e11a063970aed1ad143b9284a79c7 (diff) | |
mm/slub.c: init_on_free=1 should wipe freelist ptr for bulk allocations
slab_alloc_node() already zeroed out the freelist pointer if
init_on_free was on. Thibaut Sautereau noticed that the same needs to
be done for kmem_cache_alloc_bulk(), which performs the allocations
separately.
kmem_cache_alloc_bulk() is currently used in two places in the kernel,
so this change is unlikely to have a major performance impact.
SLAB doesn't require a similar change, as auto-initialization makes the
allocator store the freelist pointers off-slab.
Link: http://lkml.kernel.org/r/20191007091605.30530-1-glider@google.com
Fixes: 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options")
Signed-off-by: Alexander Potapenko <glider@google.com>
Reported-by: Thibaut Sautereau <thibaut@sautereau.fr>
Reported-by: Kees Cook <keescook@chromium.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Laura Abbott <labbott@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/slub.c | 22 |
1 files changed, 16 insertions, 6 deletions
diff --git a/mm/slub.c b/mm/slub.c index 442f111d1e98..b25c807a111f 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2672,6 +2672,17 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, } /* + * If the object has been wiped upon free, make sure it's fully initialized by + * zeroing out freelist pointer. + */ +static __always_inline void maybe_wipe_obj_freeptr(struct kmem_cache *s, + void *obj) +{ + if (unlikely(slab_want_init_on_free(s)) && obj) + memset((void *)((char *)obj + s->offset), 0, sizeof(void *)); +} + +/* * Inlined fastpath so that allocation functions (kmalloc, kmem_cache_alloc) * have the fastpath folded into their functions. So no function call * overhead for requests that can be satisfied on the fastpath. @@ -2759,12 +2770,8 @@ redo: prefetch_freepointer(s, next_object); stat(s, ALLOC_FASTPATH); } - /* - * If the object has been wiped upon free, make sure it's fully - * initialized by zeroing out freelist pointer. - */ - if (unlikely(slab_want_init_on_free(s)) && object) - memset(object + s->offset, 0, sizeof(void *)); + + maybe_wipe_obj_freeptr(s, object); if (unlikely(slab_want_init_on_alloc(gfpflags, s)) && object) memset(object, 0, s->object_size); @@ -3178,10 +3185,13 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, goto error; c = this_cpu_ptr(s->cpu_slab); + maybe_wipe_obj_freeptr(s, p[i]); + continue; /* goto for-loop */ } c->freelist = get_freepointer(s, object); p[i] = object; + maybe_wipe_obj_freeptr(s, p[i]); } c->tid = next_tid(c->tid); local_irq_enable(); |