linux-kernel - Re: [PATCH v2] edac_mc: Cleanup per-dimm

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Date:	Mon, 30 Apr 2012 13:47:02 -0300
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	Joe Perches <joe@...ches.com>
CC:	Linux Edac Mailing List <linux-edac@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Doug Thompson <norsk5@...oo.com>
Subject: Re: [PATCH v2] edac_mc: Cleanup per-dimm_info debug messages

Em 30-04-2012 13:16, Joe Perches escreveu:
> On Mon, 2012-04-30 at 12:02 -0300, Mauro Carvalho Chehab wrote:
>> The edac_mc_alloc() routine allocates one dimm_info device for all
>> possible memories, including the non-filled ones. The debug messages
>> there are somewhat confusing. So, cleans them, by moving the code
>> that prints the memory location to edac_mc, and using it on both
>> edac_mc_sysfs and edac_mc.
> []
>> diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
> []
>> @@ -40,6 +40,25 @@
>>  static DEFINE_MUTEX(mem_ctls_mutex);
>>  static LIST_HEAD(mc_devices);
>>  
>> +unsigned edac_dimm_info_location(struct dimm_info *dimm, char *buf,
>> +			         int len)
>> +{
>> +	struct mem_ctl_info *mci = dimm->mci;
>> +	int i, n, count = 0;
>> +	char *p = buf;
>> +
>> +	for (i = 0; i < mci->n_layers; i++) {
>> +		n = snprintf(p, len, "%s %d ",
>> +			      edac_layer_name[mci->layers[i].type],
>> +			      dimm->location[i]);
>> +		p += n;
>> +		len -= n;
>> +		count += n;
>> +	}
> 
> I believe this snprintf can be unsafe
> when the buffer length len is exceeded.
> 
> if len is negative, it's promoted to size_t
> and continues to write into p.

Ok, I've changed it to unsigned at the new version and added a break
to prevent this condition to happen. Version 3 with this fix and some
other improvements were sent.

Yet, this condition will never happen, in practice, as the edac core
currently supports only 3 layers.

Regards,
Mauro.
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