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

[Yuntao Wang <yuntao.wang@linux.dev>]

On Tue, 11 Nov 2025 10:56:51 -0600, Rob Herring <robh@kernel.org> wrote:

> On Wed, Nov 5, 2025 at 3:02 AM Yuntao Wang <yuntao.wang@linux.dev> 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.

Hi Rob,

The link to the new patch series:

https://lore.kernel.org/linux-devicetree/20251112143520.233870-11-yuntao.wang@linux.dev/t/

Thanks,
Yuntao

> > 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@glider.be>
> > Signed-off-by: Yuntao Wang <yuntao.wang@linux.dev>
> > ---
> > 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