[PATCH 3/3] libfdt: Check fdt_offset_ptr() return value unconditionally

[Simon Glass]

Hi Marek,

On Thu, 13 Nov 2025 at 05:22, Marek Vasut
<marek.vasut+renesas at mailbox.org> wrote:
>
> The fdt_offset_ptr() may return NULL pointer, check the return
> value from fdt_offset_ptr() for NULL unconditionally to prevent
> sandbox crashes.
>
> Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
> ---
> Cc: Adriano Cordova <adrianox at gmail.com>
> Cc: Andrew Goodbody <andrew.goodbody at linaro.org>
> Cc: Christian Marangi <ansuelsmth at gmail.com>
> Cc: Heinrich Schuchardt <xypron.glpk at gmx.de>
> Cc: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> Cc: Patrice Chotard <patrice.chotard at foss.st.com>
> Cc: Sam Edwards <cfsworks at gmail.com>
> Cc: Simon Glass <sjg at chromium.org>
> Cc: Tom Rini <trini at konsulko.com>
> Cc: u-boot at lists.denx.de
> ---
>  scripts/dtc/libfdt/fdt.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/dtc/libfdt/fdt.c b/scripts/dtc/libfdt/fdt.c
> index 95f644c31f9..d16cc3d4730 100644
> --- a/scripts/dtc/libfdt/fdt.c
> +++ b/scripts/dtc/libfdt/fdt.c
> @@ -168,7 +168,7 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
>
>         *nextoffset = -FDT_ERR_TRUNCATED;
>         tagp = fdt_offset_ptr(fdt, offset, FDT_TAGSIZE);
> -       if (!can_assume(VALID_DTB) && !tagp)
> +       if (!tagp)
>                 return FDT_END; /* premature end */
>         tag = fdt32_to_cpu(*tagp);
>         offset += FDT_TAGSIZE;
> @@ -186,7 +186,7 @@ uint32_t fdt_next_tag(const void *fdt, int startoffset, int *nextoffset)
>
>         case FDT_PROP:
>                 lenp = fdt_offset_ptr(fdt, offset, sizeof(*lenp));
> -               if (!can_assume(VALID_DTB) && !lenp)
> +               if (!lenp)
>                         return FDT_END; /* premature end */
>
>                 len = fdt32_to_cpu(*lenp);
> --
> 2.51.0
>

The can_assume() is there to be respected and helps to reduce code
size. What problem are you actually seeing?

Regards,
Simon