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Re: [PATCH] docs/designs: re-work the xenstore migration document...


On 24/04/2020 16:59, Jürgen Groß wrote:
On 24.04.20 17:44, Julien Grall wrote:
If I extend the record and do a downgrade I'm losing the information,
too, as the old version won't read it in any case. BTW, extending the
record is no problem, as the length is stored in the header. Unknown
records (and extensions) will be just ignored when reading.

That's very much up to the implementation. An implementation may decide to bail out if the record is not an exact size.

In your case when reusing the paddings and doing a downgrade you would
crash, as the paddings are no longer zero.

In case a downgrade should not be done due to vital information loss
then you should just not do it.

Of course, however I don't think a user will necessarily know it should not do it. So how do you protect against misuse?


Julien Grall



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