Re: [PATCH 2/2] random: add fork_event sysctl for polling VM forks

Alexander Graf
2022-05-02T18:56:35Z

On 02.05.22 20:46, Jason A. Donenfeld wrote:
> On Mon, May 02, 2022 at 08:34:38PM +0200, Alexander Graf wrote:
>> Michael, since we already changed the CID in the spec, can we add a
>> property to the device that indicates the first 4 bytes of the UUID will
>> always be different between parent and child?
>>
>> That should give us the ability to mmap the vmgenid directly to user
>> space and act based on a simple u32 compare for clone notification, no?
> That is not a good idea. We want an _additional_ 4 bytes, so that we can
> keep the first 16 bytes (128 bits) as a kernel space secret.

An additional 4 bytes would be an additional 4kb (or 64kb on ARM) page.
Do we really rely on these 16 bytes to reseed after clone? If so, we'd
need to bite the bullet and provide an additional page, yes.

Alex

Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879