Re: [PATCH mm 3/4] kasan: simplify saving extra info into tracks

[Marco Elver]

On Thu, 21 Dec 2023 at 19:35, <andrey.konovalov@xxxxxxxxx> wrote:
>
> From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>
> Avoid duplicating code for saving extra info into tracks: reuse the
> common function for this.
>
> Fixes: 5d4c6ac94694 ("kasan: record and report more information")

Looking at this patch and the previous ones, is this Fixes really
needed? I.e. was the previous patch broken?

> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Reviewed-by: Marco Elver <elver@xxxxxxxxxx>

> ---
>  mm/kasan/common.c  | 12 ++++++++++--
>  mm/kasan/generic.c |  4 ++--
>  mm/kasan/kasan.h   |  3 ++-
>  mm/kasan/tags.c    | 17 +----------------
>  4 files changed, 15 insertions(+), 21 deletions(-)
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index fe6c4b43ad9f..d004a0f4406c 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -48,7 +48,7 @@ depot_stack_handle_t kasan_save_stack(gfp_t flags, depot_flags_t depot_flags)
>         return stack_depot_save_flags(entries, nr_entries, flags, depot_flags);
>  }
>
> -void kasan_set_track(struct kasan_track *track, gfp_t flags)
> +void kasan_set_track(struct kasan_track *track, depot_stack_handle_t stack)
>  {
>  #ifdef CONFIG_KASAN_EXTRA_INFO
>         u32 cpu = raw_smp_processor_id();
> @@ -58,8 +58,16 @@ void kasan_set_track(struct kasan_track *track, gfp_t flags)
>         track->timestamp = ts_nsec >> 3;
>  #endif /* CONFIG_KASAN_EXTRA_INFO */
>         track->pid = current->pid;
> -       track->stack = kasan_save_stack(flags,
> +       track->stack = stack;
> +}
> +
> +void kasan_save_track(struct kasan_track *track, gfp_t flags)
> +{
> +       depot_stack_handle_t stack;
> +
> +       stack = kasan_save_stack(flags,
>                         STACK_DEPOT_FLAG_CAN_ALLOC | STACK_DEPOT_FLAG_GET);
> +       kasan_set_track(track, stack);
>  }
>
>  #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
> diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c
> index 769e43e05d0b..11b575707b05 100644
> --- a/mm/kasan/generic.c
> +++ b/mm/kasan/generic.c
> @@ -553,7 +553,7 @@ void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
>         stack_depot_put(alloc_meta->aux_stack[1]);
>         __memset(alloc_meta, 0, sizeof(*alloc_meta));
>
> -       kasan_set_track(&alloc_meta->alloc_track, flags);
> +       kasan_save_track(&alloc_meta->alloc_track, flags);
>  }
>
>  void kasan_save_free_info(struct kmem_cache *cache, void *object)
> @@ -564,7 +564,7 @@ void kasan_save_free_info(struct kmem_cache *cache, void *object)
>         if (!free_meta)
>                 return;
>
> -       kasan_set_track(&free_meta->free_track, 0);
> +       kasan_save_track(&free_meta->free_track, 0);
>         /* The object was freed and has free track set. */
>         *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREETRACK;
>  }
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 9072ce4c1263..31fb6bb26fed 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -372,7 +372,8 @@ static inline void kasan_init_object_meta(struct kmem_cache *cache, const void *
>  #endif
>
>  depot_stack_handle_t kasan_save_stack(gfp_t flags, depot_flags_t depot_flags);
> -void kasan_set_track(struct kasan_track *track, gfp_t flags);
> +void kasan_set_track(struct kasan_track *track, depot_stack_handle_t stack);
> +void kasan_save_track(struct kasan_track *track, gfp_t flags);
>  void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags);
>  void kasan_save_free_info(struct kmem_cache *cache, void *object);
>
> diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
> index c4d14dbf27c0..d65d48b85f90 100644
> --- a/mm/kasan/tags.c
> +++ b/mm/kasan/tags.c
> @@ -94,17 +94,6 @@ void __init kasan_init_tags(void)
>         }
>  }
>
> -#ifdef CONFIG_KASAN_EXTRA_INFO
> -static void save_extra_info(struct kasan_stack_ring_entry *entry)
> -{
> -       u32 cpu = raw_smp_processor_id();
> -       u64 ts_nsec = local_clock();
> -
> -       entry->track.cpu = cpu;
> -       entry->track.timestamp = ts_nsec >> 3;
> -}
> -#endif /* CONFIG_KASAN_EXTRA_INFO */
> -
>  static void save_stack_info(struct kmem_cache *cache, void *object,
>                         gfp_t gfp_flags, bool is_free)
>  {
> @@ -137,11 +126,7 @@ static void save_stack_info(struct kmem_cache *cache, void *object,
>         old_stack = entry->track.stack;
>
>         entry->size = cache->object_size;
> -       entry->track.pid = current->pid;
> -       entry->track.stack = stack;
> -#ifdef CONFIG_KASAN_EXTRA_INFO
> -       save_extra_info(entry);
> -#endif /* CONFIG_KASAN_EXTRA_INFO */
> +       kasan_set_track(&entry->track, stack);
>         entry->is_free = is_free;
>
>         entry->ptr = object;
> --
> 2.25.1
>