From a98fdcef941e107eeabae622d85a1f476f25a160 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 15 Jan 2008 00:02:37 +0300 Subject: [PATCH] fix the "remove task_ppid_nr_ns" commit Commit 84427eaef1fb91704c7112bdb598c810003b99f3 (remove task_ppid_nr_ns) moved the task_tgid_nr_ns(task->real_parent) outside of lock_task_sighand(). This is wrong, ->real_parent could be freed/reused. Both ->parent/real_parent point to nothing after __exit_signal() because we remove the child from ->children list, and thus the child can't be reparented when its parent exits. rcu_read_lock() protects ->parent/real_parent, but _only_ if we know it was valid before we take rcu lock. Revert this part of the patch. Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds --- fs/proc/array.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/proc/array.c b/fs/proc/array.c index 810eb8fd6500..eb97f2897e2b 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -426,7 +426,6 @@ static int do_task_stat(struct task_struct *task, char *buffer, int whole) cgtime = gtime = cputime_zero; rcu_read_lock(); - ppid = task_tgid_nr_ns(task->real_parent, ns); if (lock_task_sighand(task, &flags)) { struct signal_struct *sig = task->signal; @@ -465,6 +464,7 @@ static int do_task_stat(struct task_struct *task, char *buffer, int whole) } sid = task_session_nr_ns(task, ns); + ppid = task_tgid_nr_ns(task->real_parent, ns); pgid = task_pgrp_nr_ns(task, ns); unlock_task_sighand(task, &flags); -- 2.20.1