Re: [PATCH OLK-5.10 v3 1/4] md/raid10: fix slab-out-of-bounds in md_bitmap_get_counter

[Song Liu]

On Mon, May 15, 2023 at 6:49 AM <linan666@xxxxxxxxxxxxxxx> wrote:
>
> From: Li Nan <linan122@xxxxxxxxxx>
>
> If we write a large number to md/bitmap_set_bits, md_bitmap_checkpage()
> will return -EINVAL because 'page >= bitmap->pages', but the return value
> was not checked immediately in md_bitmap_get_counter() in order to set
> *blocks value and slab-out-of-bounds occurs.
>
> Move check of 'page >= bitmap->pages' to md_bitmap_get_counter() and
> return directly if true.
>
> Fixes: ef4256733506 ("md/bitmap: optimise scanning of empty bitmaps.")
> Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
> Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> ---
>  drivers/md/md-bitmap.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
> index 920bb68156d2..e122b19c124d 100644
> --- a/drivers/md/md-bitmap.c
> +++ b/drivers/md/md-bitmap.c
> @@ -46,6 +46,7 @@ static inline char *bmname(struct bitmap *bitmap)
>   *
>   * if we find our page, we increment the page's refcount so that it stays
>   * allocated while we're using it
> + * the caller must make sure 'page < bimap->pages'
>   */

I removed this comment, and added WARN_ON_ONCE().

Thanks,
Song

>  static int md_bitmap_checkpage(struct bitmap_counts *bitmap,
>                                unsigned long page, int create, int no_hijack)
> @@ -54,14 +55,6 @@ __acquires(bitmap->lock)
>  {
>         unsigned char *mappage;
>
> -       if (page >= bitmap->pages) {
> -               /* This can happen if bitmap_start_sync goes beyond
> -                * End-of-device while looking for a whole page.
> -                * It is harmless.
> -                */
> -               return -EINVAL;
> -       }
> -
>         if (bitmap->bp[page].hijacked) /* it's hijacked, don't try to alloc */
>                 return 0;
>
> @@ -1387,6 +1380,14 @@ __acquires(bitmap->lock)
>         sector_t csize;
>         int err;
>
> +       if (page >= bitmap->pages) {
> +               /*
> +                * This can happen if bitmap_start_sync goes beyond
> +                * End-of-device while looking for a whole page or
> +                * user set a huge number to sysfs bitmap_set_bits.
> +                */
> +               return NULL;
> +       }
>         err = md_bitmap_checkpage(bitmap, page, create, 0);
>
>         if (bitmap->bp[page].hijacked ||
> --
> 2.31.1
>