Re: [RFC] efivars write(2) races

[Lingzhu Xiang]

On 01/28/2013 08:38 PM, Matt Fleming wrote:
> On Mon, 2013-01-28 at 10:38 +0800, Lingzhu Xiang wrote:
>> On 01/25/2013 09:18 PM, Matt Fleming wrote:
>>>> 4. EFI_VARIABLE_APPEND_WRITE with EFI_OUT_OF_RESOURCES truncates size but you
>>>>      can still read its content.
>>>
>>> I'm not sure what you mean by this. Could you please explain?
>>
>> Oops, this one is incorrect. I was testing EFI_VARIABLE_APPEND_WRITE
>> using this:
>>
>> printf "\x47\x00\x00\x00\x00" >test-1-$guid
>>
>> So it truncates the file before writing, but efivarfs figures out the right
>> size afterwards. The size remains zero if the write fails.
>>
>> I should be using this for appending:
>>
>> printf "\x47\x00\x00\x00\x00" >>test-1-$guid
> 
> Does this mean that these two test cases work as expected?

Mostly yes.

printf "\x47\x00\x00\x00\x00" >test-1-$guid

still shows unexpected truncate behavior. But this is the same one
already noted previously (truncate doesn't actually work). 
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