Re: [PATCH v2] of: fdt: Fix the len check in early_init_dt_check_for_elfcorehdr()

[Rob Herring]

On Wed, Nov 5, 2025 at 3:02 AM Yuntao Wang <yuntao.wang@xxxxxxxxx> wrote:
>
> The len value is in bytes, while `dt_root_addr_cells + dt_root_size_cells`
> is in cells (4 bytes per cell).
>
> Comparing them directly is incorrect. Convert units before comparison.

We have 3 copies of the same code. This one plus "linux,kho-fdt" and
"linux,kho-scratch". Please consolidate them. The few places we have
for this type of mismatch, the better.

>
> Fixes: f7e7ce93aac1 ("of: fdt: Add generic support for handling elf core headers property")
> Fixes: e62aaeac426ab1dd ("arm64: kdump: provide /proc/vmcore file")
> Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Signed-off-by: Yuntao Wang <yuntao.wang@xxxxxxxxx>
> ---
> v1 -> v2: Add a new Fixes tag as suggested by Geert Uytterhoeven
>
>  drivers/of/fdt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 0edd639898a6..f79461f5cffc 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -812,6 +812,7 @@ static void __init early_init_dt_check_for_initrd(unsigned long node)
>   */
>  static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
>  {
> +       int t_len = (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32);
>         const __be32 *prop;
>         int len;
>
> @@ -821,7 +822,7 @@ static void __init early_init_dt_check_for_elfcorehdr(unsigned long node)
>         pr_debug("Looking for elfcorehdr property... ");
>
>         prop = of_get_flat_dt_prop(node, "linux,elfcorehdr", &len);
> -       if (!prop || (len < (dt_root_addr_cells + dt_root_size_cells)))
> +       if (!prop || len < t_len)
>                 return;
>
>         elfcorehdr_addr = dt_mem_next_cell(dt_root_addr_cells, &prop);
> --
> 2.51.0