On 12/13/2016 02:38 PM, David Howells wrote:
> Michael Kerrisk (man-pages) <mtk.manpages@xxxxxxxxx> wrote:
>
>> So, I've updated this piece a couple of times since the draft that you
>> reviewed, and by now it reads:
>>
>> "big_key" (since Linux 3.13)
>> This key type is similar to the "user" key type, but it may
>> hold a payload of up to 1 MiB in size. This key type is
>> useful for tasks such as holding Kerberos ticket caches.
>
> I'm not sure that "tasks" is quite the word I'd use here (it's overloaded).
> Perhaps "purposes"?
Fixed.
>> The payload data may be stored in the swap space rather
>> than in kernel memory if the data size exceeds the overhead
>> of storing the data encrypted in swap space. (A tmpfs file
>> is used, which requires filesystem structures to be allo‐
>> cated in the kernel; The size of these structures deter‐
>> mines the size threshold above which the tmpfs storage
>> method is used.) Since Linux 4.8, payload data is
>> encrypted, to prevent it being written unencrypted into
>> swap space.
>
> I would either drop the first "encrypted" ("storing the data encrypted") since
I already dropped that first "encrypted".
> you mention this later or move it earlier to be after the word "stored" ("may
> be stored encrypted").
>
> Note that with the "Since Linux 4.8 ..." sentence, the encryption is only
> applied if it is stored into tmpfs.
Thanks for that tip.
> Also, the payload isn't directly stored into swapspace, but is rather stored
> into tmpfs, from where it can be swapped. This is important since you can use
> this type of key without any swapspace available to your system.
Yes, the text still needs some work... How about:
"big_key" (since Linux 3.13)
This key type is similar to the "user" key type, but it may
hold a payload of up to 1 MiB in size. This key type is
useful for purposes such as holding Kerberos ticket caches.
The payload data may be stored in a tmpfs filesystem,
rather than in kernel memory, if the data size exceeds the
overhead of storing the data in the filesystem. (Storing
the data in a filesystem requires filesystem structures to
be allocated in the kernel. The size of these structures
determines the size threshold above which the tmpfs storage
method is used.) Since Linux 4.8, the payload data is
encrypted when stored in tmpfs, to prevent it being written
unencrypted into swap space.
?
Thanks,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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