Re: [PATCH] loader/efi/fdt: Ensure FDT blob is 8-byte aligned

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Add maintainers into CC

On Wed, Feb 25, 2026 at 2:07=E2=80=AFPM <[email protected]> wrote:

> From: Mikhail Lappo <[email protected]>
>
> libfdt requires the FDT blob to be 8-byte aligned. The alignment is
> validated in fdt_check_header(), and misaligned blobs may be rejected
> or cause failures on architectures that enforce strict alignment.
>
> Currently the blob is allocated with grub_malloc(), which does not
> guarantee 8-byte alignment. Replace it with grub_memalign(8, size)
> to ensure the required alignment.
>
> Signed-off-by: Mikhail Lappo <[email protected]>
> ---
>  grub-core/loader/efi/fdt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/grub-core/loader/efi/fdt.c b/grub-core/loader/efi/fdt.c
> index e510b3491..f25d362d3 100644
> --- a/grub-core/loader/efi/fdt.c
> +++ b/grub-core/loader/efi/fdt.c
> @@ -38,6 +38,7 @@ static void *fdt;
>  #define FDT_ADDR_SIZE_EXTRA ((2 * grub_fdt_prop_entry_size
> (sizeof(grub_uint32_t))) + \
>                               sizeof (FDT_ADDR_CELLS_STRING) + \
>                               sizeof (FDT_SIZE_CELLS_STRING))
> +#define FDT_BLOB_ALIGNMENT 8
>
>  static const struct grub_arg_option options_fdtdump[] =3D {
>    {"prop",     'p', 0, N_("Get property."), N_("prop"), ARG_TYPE_STRING}=
,
> @@ -145,7 +146,7 @@ grub_cmd_devicetree (grub_command_t cmd __attribute__
> ((unused)),
>      goto out;
>
>    size =3D grub_file_size (dtb);
> -  blob =3D grub_malloc (size);
> +  blob =3D grub_memalign (FDT_BLOB_ALIGNMENT, size);
>    if (!blob)
>      goto out;
>
> --
> 2.44.0
>
>

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<div dir=3D"ltr"><div>Add maintainers into CC</div><br><div class=3D"gmail_=
quote gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, =
Feb 25, 2026 at 2:07=E2=80=AFPM &lt;<a href=3D"mailto:[email protected]"=
>[email protected]</a>&gt; wrote:<br></div><blockquote class=3D"gmail_qu=
ote" style=3D"margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-st=
yle:solid;border-left-color:rgb(204,204,204);padding-left:1ex">From: Mikhai=
l Lappo &lt;<a href=3D"mailto:[email protected]" target=3D"_blank">mikle=
[email protected]</a>&gt;<br>
<br>
libfdt requires the FDT blob to be 8-byte aligned. The alignment is<br>
validated in fdt_check_header(), and misaligned blobs may be rejected<br>
or cause failures on architectures that enforce strict alignment.<br>
<br>
Currently the blob is allocated with grub_malloc(), which does not<br>
guarantee 8-byte alignment. Replace it with grub_memalign(8, size)<br>
to ensure the required alignment.<br>
<br>
Signed-off-by: Mikhail Lappo &lt;<a href=3D"mailto:[email protected]" ta=
rget=3D"_blank">[email protected]</a>&gt;<br>
---<br>
=C2=A0grub-core/loader/efi/fdt.c | 3 ++-<br>
=C2=A01 file changed, 2 insertions(+), 1 deletion(-)<br>
<br>
diff --git a/grub-core/loader/efi/fdt.c b/grub-core/loader/efi/fdt.c<br>
index e510b3491..f25d362d3 100644<br>
--- a/grub-core/loader/efi/fdt.c<br>
+++ b/grub-core/loader/efi/fdt.c<br>
@@ -38,6 +38,7 @@ static void *fdt;<br>
=C2=A0#define FDT_ADDR_SIZE_EXTRA ((2 * grub_fdt_prop_entry_size (sizeof(gr=
ub_uint32_t))) + \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 sizeof (FDT_ADDR_CELLS_STRING) + \<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 sizeof (FDT_SIZE_CELLS_STRING))<br>
+#define FDT_BLOB_ALIGNMENT 8<br>
<br>
=C2=A0static const struct grub_arg_option options_fdtdump[] =3D {<br>
=C2=A0 =C2=A0{&quot;prop&quot;,=C2=A0 =C2=A0 =C2=A0&#39;p&#39;, 0, N_(&quot=
;Get property.&quot;), N_(&quot;prop&quot;), ARG_TYPE_STRING},<br>
@@ -145,7 +146,7 @@ grub_cmd_devicetree (grub_command_t cmd __attribute__ (=
(unused)),<br>
=C2=A0 =C2=A0 =C2=A0goto out;<br>
<br>
=C2=A0 =C2=A0size =3D grub_file_size (dtb);<br>
-=C2=A0 blob =3D grub_malloc (size);<br>
+=C2=A0 blob =3D grub_memalign (FDT_BLOB_ALIGNMENT, size);<br>
=C2=A0 =C2=A0if (!blob)<br>
=C2=A0 =C2=A0 =C2=A0goto out;<br>
<br>
-- <br>
2.44.0<br>
<br>
</blockquote></div></div>

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