Re: [PATCH] block: avoid false positive warnings on ioctl to partition

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> Therefore, this patch silently blocks all ioctls except SG_IO, since
> all of them turned out to be false positives; in case some escaped, it
> should be easily diagnosable or at least bisectable.  The warning text
> is separated for root and non-root, and the deprecation period for root
> users is set to end a year from now.

NAK.

Firstly blocking CAP_SYS_RAWIO access by any means to a partition is
itself nonsense as the process has enough privilege to go poke the
controller I/O registers by hand. That's a gratuitious API breakage.

Secondly SG_IO allows users to read and write blocks outside their partition as
far as I can see from the verify logic. You either need to block it or
smarten up the filter.

What were the SG_IO command blocks that were caught ? It's going to be
pretty trivial to add a filter->partition_ok to some of them if need be.

Anyway it fails both by stopping valid stuff and not stopping insecure and
unsafe stuff.

Alan