while checking recent commits to the kernel core i took a look at the PID namespaces implementation, and it has a fatal flaw: it breaks futexes and various libraries (and other stuff) that use PIDs as the means of identifying tasks, by not providing any means of global identification that works across PID namespaces. (PIDs _are_ a very convenient and global way of identifying contexts.)
i asked Ulrich about this and it turns out he has warned about this early on: http://www.nabble.com/Re%3A-question%3A-pid-space-semantics.-p3409990.html but this problem is still present in the code, and it has been recently committed into mainline via: commit 30e49c263e36341b60b735cbef5ca37912549264 Author: Pavel Emelyanov <[EMAIL PROTECTED]> Date: Thu Oct 18 23:40:10 2007 -0700 pid namespaces: allow cloning of new namespace without these problems having been resolved. A full-scale revert is probably too intrusive, but at minimum we need to turn off user-space access to this feature via this simple patch. Until this issue is resolved properly the new PID namespace code needs to be turned off. Letting this into 2.6.24 would be a disaster. Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]> --- kernel/fork.c | 8 ++++++++ 1 file changed, 8 insertions(+) Index: v/kernel/fork.c =================================================================== --- v.orig/kernel/fork.c +++ v/kernel/fork.c @@ -1420,6 +1420,14 @@ long do_fork(unsigned long clone_flags, int trace = 0; long nr; + /* + * PID namespaces are broken at the moment: they do not allow + * certain PID based syscalls (such as futexes) to be used + * across namespaces. This is broken and must not be allowed, + * so we keep this feature turned off until it's properly fixed. + */ + clone_flags &= ~CLONE_NEWPID; + if (unlikely(current->ptrace)) { trace = fork_traceflag (clone_flags); if (trace) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
