[PATCH 1/3 for 2.6.38] oom: oom_kill_process: don't set TIF_MEMDIE if !p->mm

[Oleg Nesterov <oleg@redhat.com>]

oom_kill_process() simply sets TIF_MEMDIE and returns if PF_EXITING.
This is very wrong by many reasons. In particular, this thread can
be the dead group leader. Check p->mm != NULL.

Note: this is _not_ enough. Just a minimal fix.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

 mm/oom_kill.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 38/mm/oom_kill.c~1_kill_fix_pf_exiting	2011-03-14 17:53:05.000000000 +0100
+++ 38/mm/oom_kill.c	2011-03-14 18:51:49.000000000 +0100
@@ -470,7 +470,7 @@ static int oom_kill_process(struct task_
 	 * If the task is already exiting, don't alarm the sysadmin or kill
 	 * its children or threads, just set TIF_MEMDIE so it can die quickly
 	 */
-	if (p->flags & PF_EXITING) {
+	if (p->flags & PF_EXITING && p->mm) {
 		set_tsk_thread_flag(p, TIF_MEMDIE);
 		boost_dying_task_prio(p, mem);
 		return 0;