Upstream is erring on the side of caution though they say a resonable configuration should be protected. Pappy's already added fixes. Fixed in hardened-sources-2.4.34 and hardened-sources-2.6.19-r5
This bug no longer applies to any hardened-sources in portage and should be closed.
Good catch.
CVE-2007-0257: Unspecified vulnerability in the expand_stack function in grsecurity PaX allows local users to gain privileges via unspecified vectors. NOTE: the grsecurity developer has disputed this issue, stating that "the function they claim the vulnerability to be in is a trivial function, which can, and has been, easily checked for any supposed vulnerabilities." The developer also cites a past disclosure that was not proven. As of 20070120, the original researcher has released demonstration code.