kasan: memset free track in qlink_free

Instead of only zeroing out the stack depot handle when evicting the
free stack trace in qlink_free, zero out the whole track.

Do this just to produce a similar effect for alloc and free meta. The
other fields of the free track besides the stack trace handle are
considered invalid at this point anyway, so no harm in zeroing them out.

Link: https://lkml.kernel.org/r/db987c1cd011547e85353b0b9997de190c97e3e6.1703020707.git.andreyknvl@google.com
Fixes: 773688a ("kasan: use stack_depot_put for Generic mode")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/kasan/quarantine.c

@@ -157,7 +157,7 @@ static void qlink_free(struct qlist_node *qlink, struct kmem_cache *cache)
  if (free_meta &&
  *(u8 *)kasan_mem_to_shadow(object) == KASAN_SLAB_FREETRACK) {
  stack_depot_put(free_meta->free_track.stack);
- free_meta->free_track.stack = 0;
+ __memset(&free_meta->free_track, 0, sizeof(free_meta->free_track));
  }
 
  /*