| Message ID | 2805da5df4b57138fdacd671f5d227d58950ba54.1640037083.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] kasan: fix quarantine conflicting with init_on_free | expand |
On Mon, 20 Dec 2021 at 22:56, <andrey.konovalov@linux.dev> wrote: > > From: Andrey Konovalov <andreyknvl@google.com> > > KASAN's quarantine might save its metadata inside freed objects. As > this happens after the memory is zeroed by the slab allocator when > init_on_free is enabled, the memory coming out of quarantine is not > properly zeroed. > > This causes lib/test_meminit.c tests to fail with Generic KASAN. > > Zero the metadata when the object is removed from quarantine. > > Fixes: 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options") > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Marco Elver <elver@google.com> Thank you. > --- > > Changes v1->v2: > - Use memzero_explicit() instead of memset(). > --- > mm/kasan/quarantine.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c > index 587da8995f2d..08291ed33e93 100644 > --- a/mm/kasan/quarantine.c > +++ b/mm/kasan/quarantine.c > @@ -132,11 +132,22 @@ static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache) > static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache) > { > void *object = qlink_to_object(qlink, cache); > + struct kasan_free_meta *meta = kasan_get_free_meta(cache, object); > unsigned long flags; > > if (IS_ENABLED(CONFIG_SLAB)) > local_irq_save(flags); > > + /* > + * If init_on_free is enabled and KASAN's free metadata is stored in > + * the object, zero the metadata. Otherwise, the object's memory will > + * not be properly zeroed, as KASAN saves the metadata after the slab > + * allocator zeroes the object. > + */ > + if (slab_want_init_on_free(cache) && > + cache->kasan_info.free_meta_offset == 0) > + memzero_explicit(meta, sizeof(*meta)); > + > /* > * As the object now gets freed from the quarantine, assume that its > * free track is no longer valid. > -- > 2.25.1 >
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c index 587da8995f2d..08291ed33e93 100644 --- a/mm/kasan/quarantine.c +++ b/mm/kasan/quarantine.c @@ -132,11 +132,22 @@ static void *qlink_to_object(struct qlist_node *qlink, struct kmem_cache *cache) static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache) { void *object = qlink_to_object(qlink, cache); + struct kasan_free_meta *meta = kasan_get_free_meta(cache, object); unsigned long flags; if (IS_ENABLED(CONFIG_SLAB)) local_irq_save(flags); + /* + * If init_on_free is enabled and KASAN's free metadata is stored in + * the object, zero the metadata. Otherwise, the object's memory will + * not be properly zeroed, as KASAN saves the metadata after the slab + * allocator zeroes the object. + */ + if (slab_want_init_on_free(cache) && + cache->kasan_info.free_meta_offset == 0) + memzero_explicit(meta, sizeof(*meta)); + /* * As the object now gets freed from the quarantine, assume that its * free track is no longer valid.