[linux-yocto] [PATCH] [for all x86 branches] x86/boot: Save fields explicitly, zero out everything else

[Bruce Ashfield]

Since this is destined for -stable, I'm not going to merge the individual patch.

I'm holding nearly all 5.2 updates until the last introduction issues
are fixed. By that time, I'll have the next round of -stable updates
ready to go as well.

Cheers,

Bruce

On Thu, Sep 5, 2019 at 6:02 AM <zhe.he at windriver.com> wrote:
>
> From: John Hubbard <jhubbard at nvidia.com>
>
> commit a90118c445cc7f07781de26a9684d4ec58bfcfd1 upstream.
>
> Recent gcc compilers (gcc 9.1) generate warnings about an out of bounds
> memset, if the memset goes accross several fields of a struct. This
> generated a couple of warnings on x86_64 builds in sanitize_boot_params().
>
> Fix this by explicitly saving the fields in struct boot_params
> that are intended to be preserved, and zeroing all the rest.
>
> [ tglx: Tagged for stable as it breaks the warning free build there as well ]
>
> Suggested-by: Thomas Gleixner <tglx at linutronix.de>
> Suggested-by: H. Peter Anvin <hpa at zytor.com>
> Signed-off-by: John Hubbard <jhubbard at nvidia.com>
> Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
> Cc: stable at vger.kernel.org
> Link: https://lkml.kernel.org/r/20190731054627.5627-2-jhubbard@nvidia.com
> Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> ---
> Fix the following build warning. It has been merge to 5.2.11.
> Please consider merging if it's worth.
>
> ./arch/x86/include/asm/bootparam_utils.h:40:3: warning: ‘memset’ offset [197, 448] from the object at ‘boot_params’ is out of the bounds of referenced subobject ‘ext_ramdisk_image’ with type
>  ‘unsigned int’ at offset 192 [-Warray-bounds]
>
> ./arch/x86/include/asm/bootparam_utils.h:43:3: warning: ‘memset’ offset [493, 497] from the object at ‘boot_params’ is out of the bounds of referenced subobject ‘kbd_status’ with type ‘unsig
> ned char’ at offset 491 [-Warray-bounds]
>
>  arch/x86/include/asm/bootparam_utils.h | 63 ++++++++++++++++++++++++++--------
>  1 file changed, 48 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/include/asm/bootparam_utils.h b/arch/x86/include/asm/bootparam_utils.h
> index f6f6ef4..7fed0fc 100644
> --- a/arch/x86/include/asm/bootparam_utils.h
> +++ b/arch/x86/include/asm/bootparam_utils.h
> @@ -18,6 +18,20 @@
>   * Note: efi_info is commonly left uninitialized, but that field has a
>   * private magic, so it is better to leave it unchanged.
>   */
> +
> +#define sizeof_mbr(type, member) ({ sizeof(((type *)0)->member); })
> +
> +#define BOOT_PARAM_PRESERVE(struct_member)                             \
> +       {                                                               \
> +               .start = offsetof(struct boot_params, struct_member),   \
> +               .len   = sizeof_mbr(struct boot_params, struct_member), \
> +       }
> +
> +struct boot_params_to_save {
> +       unsigned int start;
> +       unsigned int len;
> +};
> +
>  static void sanitize_boot_params(struct boot_params *boot_params)
>  {
>         /*
> @@ -35,21 +49,40 @@ static void sanitize_boot_params(struct boot_params *boot_params)
>          * problems again.
>          */
>         if (boot_params->sentinel) {
> -               /* fields in boot_params are left uninitialized, clear them */
> -               boot_params->acpi_rsdp_addr = 0;
> -               memset(&boot_params->ext_ramdisk_image, 0,
> -                      (char *)&boot_params->efi_info -
> -                       (char *)&boot_params->ext_ramdisk_image);
> -               memset(&boot_params->kbd_status, 0,
> -                      (char *)&boot_params->hdr -
> -                      (char *)&boot_params->kbd_status);
> -               memset(&boot_params->_pad7[0], 0,
> -                      (char *)&boot_params->edd_mbr_sig_buffer[0] -
> -                       (char *)&boot_params->_pad7[0]);
> -               memset(&boot_params->_pad8[0], 0,
> -                      (char *)&boot_params->eddbuf[0] -
> -                       (char *)&boot_params->_pad8[0]);
> -               memset(&boot_params->_pad9[0], 0, sizeof(boot_params->_pad9));
> +               static struct boot_params scratch;
> +               char *bp_base = (char *)boot_params;
> +               char *save_base = (char *)&scratch;
> +               int i;
> +
> +               const struct boot_params_to_save to_save[] = {
> +                       BOOT_PARAM_PRESERVE(screen_info),
> +                       BOOT_PARAM_PRESERVE(apm_bios_info),
> +                       BOOT_PARAM_PRESERVE(tboot_addr),
> +                       BOOT_PARAM_PRESERVE(ist_info),
> +                       BOOT_PARAM_PRESERVE(acpi_rsdp_addr),
> +                       BOOT_PARAM_PRESERVE(hd0_info),
> +                       BOOT_PARAM_PRESERVE(hd1_info),
> +                       BOOT_PARAM_PRESERVE(sys_desc_table),
> +                       BOOT_PARAM_PRESERVE(olpc_ofw_header),
> +                       BOOT_PARAM_PRESERVE(efi_info),
> +                       BOOT_PARAM_PRESERVE(alt_mem_k),
> +                       BOOT_PARAM_PRESERVE(scratch),
> +                       BOOT_PARAM_PRESERVE(e820_entries),
> +                       BOOT_PARAM_PRESERVE(eddbuf_entries),
> +                       BOOT_PARAM_PRESERVE(edd_mbr_sig_buf_entries),
> +                       BOOT_PARAM_PRESERVE(edd_mbr_sig_buffer),
> +                       BOOT_PARAM_PRESERVE(e820_table),
> +                       BOOT_PARAM_PRESERVE(eddbuf),
> +               };
> +
> +               memset(&scratch, 0, sizeof(scratch));
> +
> +               for (i = 0; i < ARRAY_SIZE(to_save); i++) {
> +                       memcpy(save_base + to_save[i].start,
> +                              bp_base + to_save[i].start, to_save[i].len);
> +               }
> +
> +               memcpy(boot_params, save_base, sizeof(*boot_params));
>         }
>  }
>
> --
> 2.7.4
>


-- 
- Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end
- "Use the force Harry" - Gandalf, Star Trek II