Re: [Xen-devel] [PATCH v10 01/16] microcode/intel: extend microcode_update_match()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 12.09.2019 12:24, Jan Beulich wrote:
> On 12.09.2019 09:22, Chao Gao wrote:
>> --- a/xen/arch/x86/microcode_intel.c
>> +++ b/xen/arch/x86/microcode_intel.c
>> @@ -134,21 +134,11 @@ static int collect_cpu_info(unsigned int cpu_num, 
>> struct cpu_signature *csig)
>>      return 0;
>>  }
>>  
>> -static inline int microcode_update_match(
>> -    unsigned int cpu_num, const struct microcode_header_intel *mc_header,
>> -    int sig, int pf)
>> +static int microcode_sanity_check(const void *mc)
>>  {
>> -    struct ucode_cpu_info *uci = &per_cpu(ucode_cpu_info, cpu_num);
>> -
>> -    return (sigmatch(sig, uci->cpu_sig.sig, pf, uci->cpu_sig.pf) &&
>> -            (mc_header->rev > uci->cpu_sig.rev));
>> -}
>> -
>> -static int microcode_sanity_check(void *mc)
>> -{
>> -    struct microcode_header_intel *mc_header = mc;
>> -    struct extended_sigtable *ext_header = NULL;
>> -    struct extended_signature *ext_sig;
>> +    const struct microcode_header_intel *mc_header = mc;
>> +    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;
>> @@ -234,6 +224,42 @@ static int microcode_sanity_check(void *mc)
>>      return 0;
>>  }
>>  
>> +/* Check an update against the CPU signature and current update revision */
>> +static enum microcode_match_result microcode_update_match(
>> +    const struct microcode_header_intel *mc_header, unsigned int cpu)
>> +{
>> +    const struct extended_sigtable *ext_header;
>> +    const struct extended_signature *ext_sig;
>> +    unsigned int i;
>> +    struct ucode_cpu_info *uci = &per_cpu(ucode_cpu_info, cpu);
>> +    unsigned int sig = uci->cpu_sig.sig;
>> +    unsigned int pf = uci->cpu_sig.pf;
>> +    unsigned int rev = uci->cpu_sig.rev;
>> +    unsigned long data_size = get_datasize(mc_header);
>> +    const void *end = (const void *)mc_header + get_totalsize(mc_header);
>> +
>> +    ASSERT(!microcode_sanity_check(mc_header));
>> +    if ( sigmatch(sig, mc_header->sig, pf, mc_header->pf) )
>> +        return (mc_header->rev > rev) ? NEW_UCODE : OLD_UCODE;
>> +
>> +    ext_header = (const void *)(mc_header + 1) + data_size;
>> +    ext_sig = (const void *)(ext_header + 1);
>> +
>> +    /*
>> +     * Make sure there is enough space to hold an extended header and enough
>> +     * array elements.
>> +     */
>> +    if ( (end < (const void *)ext_sig) ||
>> +         (end < (const void *)(ext_sig + ext_header->count)) )
>> +        return MIS_UCODE;
> 
> With you now assuming that the blob has previously passed
> microcode_sanity_check(), this only needs to be
> 
>     if ( (end <= (const void *)ext_sig) )
>         return MIS_UCODE;
> 
> now afaict.
> 
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> preferably with this adjustment (assuming you agree).

FAOD: I'd be happy to make the adjustment while committing, but
I'd like to have your consent (or you proving me wrong). This
would, as it looks, allow everything up to patch 8 to go in.

Jan

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