linux-kernel - Re: [PATCH][next] mailbox: PCC: check for negative count for parse failure checking

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Date:   Wed, 30 May 2018 12:49:54 -0600
From:   Al Stone <ahs3@...hat.com>
To:     Colin Ian King <colin.king@...onical.com>,
        Jassi Brar <jassisinghbrar@...il.com>
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] mailbox: PCC: check for negative count for parse
 failure checking

On 05/30/2018 12:24 PM, Colin Ian King wrote:
> On 30/05/18 18:59, Al Stone wrote:
>> On 05/30/2018 11:14 AM, Colin King wrote:
>>> From: Colin Ian King <colin.king@...onical.com>
>>>
>>> The function acpi_table_parse_enties_array can potentially return a
>>> negative value if parsing fails. Currently the check on the return
>>> is not checking for errors, so fix this by adding a -ve check too.
>>>
>>> Detected by CoverityScan, CID#1469477 ("Improper use of negative value")
>>>
>>> Fixes: 8f8027c5f935 ("mailbox: PCC: erroneous error message when parsing ACPI PCCT")
>>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>>> ---
>>>  drivers/mailbox/pcc.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
>>> index fc3c237daef2..87d67922020d 100644
>>> --- a/drivers/mailbox/pcc.c
>>> +++ b/drivers/mailbox/pcc.c
>>> @@ -461,7 +461,7 @@ static int __init acpi_pcc_probe(void)
>>>  	count = acpi_table_parse_entries_array(ACPI_SIG_PCCT,
>>>  			sizeof(struct acpi_table_pcct), proc,
>>>  			ACPI_PCCT_TYPE_RESERVED, MAX_PCC_SUBSPACES);
>>> -	if (count == 0 || count > MAX_PCC_SUBSPACES) {
>>> +	if (count <= 0 || count > MAX_PCC_SUBSPACES) {
>>>  		pr_warn("Invalid PCCT: %d PCC subspaces\n", count);
>>>  		return -EINVAL;
>>>  	}
>>>
>>
>> Yup, nice catch.  A little paranoid, but we like that in a kernel :).  Thanks.
> 
> If it can go wrong, it will go wrong, especially with firmware :-)

Amen to that!  You are preachin' to the choir, brother ...

>>
>> Reviewed-by: Al Stone <ahs3@...hat.com>
>>
> 


-- 
ciao,
al
-----------------------------------
Al Stone
Software Engineer
Red Hat, Inc.
ahs3@...hat.com
-----------------------------------