SPL requires CONFIG_PAX_SIZE_OVERFLOW and CONFIG_PAX_RANDKSTACK to be disabled

[8573]

Gentoo Linux’s sys-kernel/spl-0.6.3-r1 package (and possibly earlier
versions; I don’t know) requires that the grsecurity/PaX kernel
configuration settings CONFIG_PAX_SIZE_OVERFLOW and
CONFIG_PAX_RANDKSTACK be disabled.

I’m filing this report to track this issue at @ryao’s suggestion,
after conversation in <ircs://chat.freenode.net/gentoo-hardened>:

2014-12-18 22:49:22 <c74d3> ryao: ZFS/SPL requires CONFIG_PAX_SIZE_OVERFLOW=n and CONFIG_PAX_RANDKSTACK=n now?
[…]
2014-12-18 23:01:58 <+ryao> c74d3: Changes in PAX's implementation of those options caused ZFS to break. I plan to try to fix it when I have time.
2014-12-18 23:04:01 <c74d3> ryao: Okay, thanks. Is there a corresponding GitHub issue report I could subscribe to?
2014-12-18 23:04:35 <c74d3> (Or Gentoo bug report.)
2014-12-18 23:05:57 <+ryao> c74d3: I do not think anyone has filed one yet.
2014-12-18 23:08:10 <c74d3> ryao: Okay. Should I file one?
2014-12-18 23:08:23 <+ryao> c74d3: Sure
2014-12-18 23:08:31 <c74d3> Against ZFS or SPL?
2014-12-18 23:09:03 <+ryao> c74d3: Put it in the gentoo tracker.
2014-12-18 23:09:32 <c74d3> Oh, okay. It's not considered an upstream issue?
2014-12-18 23:10:29 <+ryao> c74d3: It is, but I have no idea if it is a ZFS issue or a SPL issue. In one case, it might just be a bug in PAX...
2014-12-18 23:11:21 <+ryao> c74d3: I need to take time to try to fix it before I will know for certain. I am also the only upstream developer who writes the patches for PaX/GrSecurity.
2014-12-18 23:12:46 <+ryao> c74d3: You could file it in both upstream and Gentoo. The SPL might be the best place to file it upstream.

[8573]

Gentoo bug report: https://bugs.gentoo.org/532992.

[chrisrd]

For CONFIG_PAX_SIZE_OVERFLOW, see also openzfs/zfs#2505

[behlendorf]

Closing. It's my understanding that the outstanding PAX issues have been resolved. If that's not the case let's make sure we have open issues in the zfs tracker for any remaining problems.