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Subject: Re: [PATCH][next] mailbox: PCC: check for negative count for parse
 failure checking
To:     ahs3@redhat.com, Jassi Brar <jassisinghbrar@gmail.com>
Cc:     kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20180530171429.3172-1-colin.king@canonical.com>
 <0d780988-0e59-a3b7-a7c1-9e3f0d227412@redhat.com>
From:   Colin Ian King <colin.king@canonical.com>
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Message-ID: <905b4bfb-9fca-a165-7911-61122281e6a4@canonical.com>
Date:   Wed, 30 May 2018 19:24:19 +0100
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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@canonical.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@canonical.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 :-)
> 
> Reviewed-by: Al Stone <ahs3@redhat.com>
>