Commit a98fdcef authored Jan 15, 2008 by Oleg Nesterov Committed by Linus Torvalds Jan 14, 2008

fix the "remove task_ppid_nr_ns" commit



Commit 84427eae (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 <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 4fd3670e

fs/proc/array.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);

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