[PATCH v2] bootstage: Fix out-of-bounds read in reloc_bootstage()

[Simon Glass]

Hi Richard,

On Wed, 31 Jul 2024 at 10:08, Richard Weinberger <richard at nod.at> wrote:
>
> bootstage_get_size() returns the total size of the data structure
> including associated records.
> When copying from gd->bootstage, only the allocation size of gd->bootstage
> must be used. Otherwise too much memory is copied.
>
> This bug caused no harm so far because gd->new_bootstage is always
> large enough and reading beyond the allocation length of gd->bootstage
> caused no problem due to the U-Boot memory layout.
>
> Fix by using the correct size and perform the initial copy directly
> in bootstage_relocate() to have the whole relocation process in the
> same function.
>
> Signed-off-by: Richard Weinberger <richard at nod.at>
> ---
> Changes since v1:
> - Pass gd->new_bootstage to bootstage_relocate()
> ---
>  common/board_f.c    | 8 +-------
>  common/bootstage.c  | 8 ++++++--
>  include/bootstage.h | 4 ++--
>  3 files changed, 9 insertions(+), 11 deletions(-)
>

Reviewed-by: Simon Glass <sjg at chromium.org>

nit below

> diff --git a/common/board_f.c b/common/board_f.c
> index 29e185137a..21a8944e2b 100644
> --- a/common/board_f.c
> +++ b/common/board_f.c
> @@ -683,13 +683,7 @@ static int reloc_bootstage(void)
>         if (gd->flags & GD_FLG_SKIP_RELOC)
>                 return 0;
>         if (gd->new_bootstage) {
> -               int size = bootstage_get_size();
> -
> -               debug("Copying bootstage from %p to %p, size %x\n",
> -                     gd->bootstage, gd->new_bootstage, size);
> -               memcpy(gd->new_bootstage, gd->bootstage, size);
> -               gd->bootstage = gd->new_bootstage;
> -               bootstage_relocate();
> +               bootstage_relocate(gd->new_bootstage);
>         }
>  #endif
>
> diff --git a/common/bootstage.c b/common/bootstage.c
> index b6c268d9f4..49acc9078a 100644
> --- a/common/bootstage.c
> +++ b/common/bootstage.c
> @@ -54,12 +54,16 @@ struct bootstage_hdr {
>         u32 next_id;            /* Next ID to use for bootstage */
>  };
>
> -int bootstage_relocate(void)
> +int bootstage_relocate(void *to)
>  {
> -       struct bootstage_data *data = gd->bootstage;
> +       struct bootstage_data *data;
>         int i;
>         char *ptr;
>
> +       debug("Copying bootstage from %p to %p\n", gd->bootstage, to);
> +       memcpy(to, gd->bootstage, sizeof(struct bootstage_data));
> +       data = gd->bootstage = to;

should be a separate line (patman/checkpatch complains)

> +
>         /* Figure out where to relocate the strings to */
>         ptr = (char *)(data + 1);
>
> diff --git a/include/bootstage.h b/include/bootstage.h
> index f4e77b09d7..57792648c4 100644
> --- a/include/bootstage.h
> +++ b/include/bootstage.h
> @@ -258,7 +258,7 @@ void show_boot_progress(int val);
>   * relocation, since memory can be overwritten later.
>   * Return: Always returns 0, to indicate success
>   */
> -int bootstage_relocate(void);
> +int bootstage_relocate(void *to);
>
>  /**
>   * Add a new bootstage record
> @@ -395,7 +395,7 @@ static inline ulong bootstage_add_record(enum bootstage_id id,
>   * and won't even do that unless CONFIG_SHOW_BOOT_PROGRESS is defined
>   */
>
> -static inline int bootstage_relocate(void)
> +static inline int bootstage_relocate(void *to)
>  {
>         return 0;
>  }
> --
> 2.35.3
>

Regards,
Simon