CVE request - kernel: jfs: don't allow os2 xattr namespace overlap with others

[Eugene Teo <eugeneteo () kernel sg>]

Upstream commit: aca0fa34bdaba39bfddddba8ca70dba4782e8fe6

Description from the commit: It's currently possible to bypass xattr 
namespace access rules by prefixing valid xattr names with "os2.", since 
the os2 namespace stores extended attributes in a legacy format with no 
prefix.

This patch adds checking to deny access to any valid namespace prefix 
following "os2.".

Thanks, Eugene
--
main(i) { putchar(182623909 >> (i-1) * 5&31|!!(i<7)<<6) && main(++i); }