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

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

[Yuntao Wang]

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.

Fixes: f7e7ce93aac1 ("of: fdt: Add generic support for handling elf core headers property")
Signed-off-by: Yuntao Wang <yuntao.wang@linux.dev>
---
 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

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

[Geert Uytterhoeven]

Hi Yuntaoi,

On Sun, 2 Nov 2025 at 15:18, 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.

Thanks for your patch!

> Fixes: f7e7ce93aac1 ("of: fdt: Add generic support for handling elf core headers property")

My commit consolidated existing code, so you may want to add
Fixes: e62aaeac426ab1dd ("arm64: kdump: provide /proc/vmcore file")
so code in v5.14 and older will be fixed by stable backports, too.

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

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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

[Yuntao Wang]

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.

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

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@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.

>
> 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

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

[Yuntao Wang]

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