Re: [PATCH v2 6/7] x86/ucode/intel: Clean up microcode_sanity_check()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 27.03.2020 13:29, Andrew Cooper wrote:
> @@ -160,93 +153,85 @@ static int collect_cpu_info(struct cpu_signature *csig)
>      return 0;
>  }
>  
> -static int microcode_sanity_check(const struct microcode_patch *mc)
> +/*
> + * Sanity check a blob which is expected to be a microcode patch.  The 48 
> byte
> + * header is of a known format, and together with totalsize are within the
> + * bounds of the container.  Everything else is unchecked.
> + */
> +static int microcode_sanity_check(const struct microcode_patch *patch)
>  {
> -    const struct microcode_header_intel *mc_header = &mc->hdr;
> -    const struct extended_sigtable *ext_header = NULL;
> -    const struct extended_signature *ext_sig;
> -    unsigned long total_size, data_size, ext_table_size;
> -    unsigned int ext_sigcount = 0, i;
> -    uint32_t sum, orig_sum;
> -
> -    total_size = get_totalsize(mc);
> -    data_size = get_datasize(mc);
> -    if ( (data_size + MC_HEADER_SIZE) > total_size )
> +    const struct extended_sigtable *ext;
> +    const uint32_t *ptr;
> +    unsigned int total_size = get_totalsize(patch);
> +    unsigned int data_size = get_datasize(patch);
> +    unsigned int i, ext_size;
> +    uint32_t sum;
> +
> +    /*
> +     * Total size must be a multiple of 1024 bytes.  Data size and the header
> +     * must fit within it.
> +     */
> +    if ( (total_size & 1023) ||
> +         data_size > (total_size - MC_HEADER_SIZE) )
>      {
> -        printk(KERN_ERR "microcode: error! "
> -               "Bad data size in microcode data file\n");
> +        printk(XENLOG_WARNING "microcode: Bad size\n");
>          return -EINVAL;
>      }
>  
> -    if ( (mc_header->ldrver != 1) || (mc_header->hdrver != 1) )
> -    {
> -        printk(KERN_ERR "microcode: error! "
> -               "Unknown microcode update format\n");
> +    /* Checksum the main header and data. */
> +    for ( sum = 0, ptr = (const uint32_t *)patch;
> +          ptr < (const uint32_t *)&patch->data[data_size]; ++ptr )
> +        sum += *ptr;
> +
> +    if ( sum != 0 )
>          return -EINVAL;

The error message for this looks to have been lost, or ...

> -    }
> -    ext_table_size = total_size - (MC_HEADER_SIZE + data_size);
> -    if ( ext_table_size )
> +
> +    /* Look to see if there is an extended signature table. */
> +    ext_size = total_size - data_size - MC_HEADER_SIZE;
> +
> +    /* No extended signature table?  All done. */
> +    if ( ext_size == 0 )
>      {
> -        if ( (ext_table_size < EXT_HEADER_SIZE) ||
> -             ((ext_table_size - EXT_HEADER_SIZE) % EXT_SIGNATURE_SIZE) )
> -        {
> -            printk(KERN_ERR "microcode: error! "
> -                   "Small exttable size in microcode data file\n");
> -            return -EINVAL;
> -        }
> -        ext_header = (void *)mc + MC_HEADER_SIZE + data_size;
> -        if ( ext_table_size != exttable_size(ext_header) )
> -        {
> -            printk(KERN_ERR "microcode: error! "
> -                   "Bad exttable size in microcode data file\n");
> -            return -EFAULT;
> -        }
> -        ext_sigcount = ext_header->count;
> +        printk(XENLOG_WARNING "microcode: Bad checksum\n");
> +        return 0;

... to have got mistakenly moved here. With this addressed
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan