linux-kernel - Re: [PATCH 3/3] efi/memattr: Include EFI memmap size in corruption warnings

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Message-ID: <CAMj1kXFn7CeT6R2w_XKAJoj5WUYObOWKeUO2istY8sULQTwomQ@mail.gmail.com>
Date: Tue, 7 Jan 2025 12:24:03 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Gregory Price <gourry@...rry.net>, Usama Arif <usamaarif642@...il.com>, linux-efi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH 3/3] efi/memattr: Include EFI memmap size in corruption warnings

On Mon, 6 Jan 2025 at 20:03, Breno Leitao <leitao@...ian.org> wrote:
>
> Add EFI memory map size to warning messages when a corrupted Memory
> Attributes Table is detected, making it easier to diagnose firmware issues.
>
> Signed-off-by: Breno Leitao <leitao@...ian.org>
> ---
>  drivers/firmware/efi/memattr.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/firmware/efi/memattr.c b/drivers/firmware/efi/memattr.c
> index 5f83cdea88b05cb325e9f90c14a0048131e53cfa..2c276bcc0df48352bec6cd96b69edf67a16f6069 100644
> --- a/drivers/firmware/efi/memattr.c
> +++ b/drivers/firmware/efi/memattr.c
> @@ -22,7 +22,7 @@ unsigned long __ro_after_init efi_mem_attr_table = EFI_INVALID_TABLE_ADDR;
>  void __init efi_memattr_init(void)
>  {
>         efi_memory_attributes_table_t *tbl;
> -       unsigned long size;
> +       unsigned long size, efi_map_size;
>
>         if (efi_mem_attr_table == EFI_INVALID_TABLE_ADDR)
>                 return;
> @@ -49,9 +49,10 @@ void __init efi_memattr_init(void)
>          * just be ignored altogether.
>          */
>         size = tbl->num_entries * tbl->desc_size;
> -       if (size > 3 * efi.memmap.nr_map * efi.memmap.desc_size) {
> -               pr_warn(FW_BUG "Corrupted EFI Memory Attributes Table detected! (version == %u, desc_size == %u, num_entries == %u)\n",
> -                       tbl->version, tbl->desc_size, tbl->num_entries);
> +       efi_map_size = efi.memmap.nr_map * efi.memmap.desc_size;
> +       if (size > 3 * efi_map_size) {
> +               pr_warn(FW_BUG "Corrupted EFI Memory Attributes Table detected! (version == %u, desc_size == %u, num_entries == %u, efi_map_size == %lu)\n",
> +                       tbl->version, tbl->desc_size, tbl->num_entries, efi_map_size);
>                 goto unmap;
>         }
>
>

Hello Breno,

I don't mind the patch per se, but I don't think it is terribly useful either.

Could you explain how this helps?