Re: [tip:x86/cpu] x86/cpu: Strip any /proc/ cpuinfo model name field whitespace

Prarit Bhargava
2015-05-28T11:27:30Z

On 05/27/2015 03:16 PM, Joe Perches wrote:
> On Wed, 2015-05-27 at 21:06 +0200, Borislav Petkov wrote:
>> On Wed, May 27, 2015 at 10:07:34AM -0700, Joe Perches wrote:
>>> This code can memmove from beyond the x86_model_id field.
>>
>> ... in the theoretical case where some model ID has more than 64 - 48
>> preceding white spaces.
>>
>> I guess we want to be prepared here for insane CPU model IDs coming from
>> virtualization.
>>
>>> Maybe:
>>> char *model = strim(c->x86_model_id);
>>> memmove(c->x86_model_id, model, strlen(model) + 1);
>>
>> Yes, and additionally limit that string length:
>>
>> ---
>> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> []
>> @@ -383,6 +383,9 @@ static const struct cpu_dev *cpu_devs[X86_VENDOR_NUM] = {};
>> static void get_model_name(struct cpuinfo_x86 *c)
>> {
>> unsigned int *v;
>> + const char *model;
>> +
>> +#define MODEL_ID_MAXLEN 48
>>
>> if (c->extended_cpuid_level < 0x80000004)
>> return;
>> @@ -391,13 +394,15 @@ static void get_model_name(struct cpuinfo_x86 *c)
>> cpuid(0x80000002, &v[0], &v[1], &v[2], &v[3]);
>> cpuid(0x80000003, &v[4], &v[5], &v[6], &v[7]);
>> cpuid(0x80000004, &v[8], &v[9], &v[10], &v[11]);
>> - c->x86_model_id[48] = 0;
>> + c->x86_model_id[MODEL_ID_MAXLEN] = 0;
>>
>> /*
>> * Remove leading whitespace on Intel processors and trailing
>> * whitespace on AMD processors.
>> */
>> - memmove(c->x86_model_id, strim(c->x86_model_id), 48);
>> + model = strim(c->x86_model_id);
>> +
>> + memmove(c->x86_model_id, model, strnlen(model, MODEL_ID_MAXLEN) + 1);
>
> I don't see any value in the #define or strnlen over strlen as
> it's guaranteed terminated by the = 0 above, but <shrug> thanks.
>

FWIW, I agree with Joe here and don't think the #define is necessary.
I will post a follow-up patch against tip on LKML shortly.

P.

> cheers, Joe
>
>
>