Re: [security]: kernel ioctl()'s [2]

Albert D. Cahalan (acahalan@cs.uml.edu)
Fri, 2 Jul 1999 18:42:38 -0400 (EDT)



Chris Evans writes:

> Oh yeah. So, question, what's the ext2_i.i_version used by?
> I suppose I withdraw my objection to letting users set it!

The NFS server is supposed to use i_version. Don't think of
i_version as a file version like VMS has. The BSD name, i_gen,
more accurately indicates that this is a generation number.

The filesystem should change i_gen when and only when an inode
is allocated. Random numbers are OK, as are serial numbers.
Perhaps use 16 bits of randomness and 16 of serial number?

Without i_gen, newly created files could be confused with old
files that were just deleted. This is because the NFS cookie
could end up being the same. The addition of i_gen prevents
duplicate NFS cookie generation.

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