linux-kernel - Re: [Patch] firmware: dmi_scan: fix dmi scan to handle "End of Table" structure

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Message-ID: <54D22753.7060709@linaro.org>
Date:	Wed, 04 Feb 2015 16:06:11 +0200
From:	Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Matt Fleming <matt.fleming@...el.com>,
	Leif Lindholm <leif.lindholm@...aro.org>
Subject: Re: [Patch] firmware: dmi_scan: fix dmi scan to handle "End of Table"
 structure


On 02/04/2015 04:04 PM, Ard Biesheuvel wrote:
> On 4 February 2015 at 13:57, Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org> wrote:
>> The dmi-sysfs should create "End of Table" entry, that is type 127.
>> But after adding initial SMBIOS v3 support the 127-0 entry is not
>> handled any more, as result it's not created in sysfs.
>> This is important because the size of whole DMI table must correspond
>> to sum of all DMI entry sizes.
>>
>> Of-course, it can be handled in newly introduced libdmifs by adding
>> end entry virtually, but it's brake backward compatibility and don't
>> correspond to SMBIOS DMI table size read from SMBIOS entry point
>> structure.
>>
>> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
>> ---
>>   drivers/firmware/dmi_scan.c | 6 ------
>>   1 file changed, 6 deletions(-)
>>
>> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
>> index c5f7b4e..c63e5e5 100644
>> --- a/drivers/firmware/dmi_scan.c
>> +++ b/drivers/firmware/dmi_scan.c
>> @@ -93,12 +93,6 @@ static void dmi_table(u8 *buf, int len, int num,
>>                  const struct dmi_header *dm = (const struct dmi_header *)data;
>>
>>                  /*
>> -                * 7.45 End-of-Table (Type 127) [SMBIOS reference spec v3.0.0]
>> -                */
>> -               if (dm->type == DMI_ENTRY_END_OF_TABLE)
>> -                       break;
>> -
>> -               /*
>>                   *  We want to know the total length (formatted area and
>>                   *  strings) before decoding to make sure we won't run off the
>>                   *  table in dmi_decode or dmi_string
> This is not the right way to fix this: the end-of-table check needs to
> be done, because the v3 entry point does not contain the actual length
> of the data, but only an upper bound, and there may be trailing
> garbage.
>
> So apparently, I put this check and break in the wrong place, and we
> should place it after the decode() call instead, but not remove it.
>

Ok.
I'll send v2.
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