Re: [PATCH 06/26] rlimit: Remove unnecessary grab of tasklist_lock
flat view
From: Oleg Nesterov <oleg@redhat.com>
Date: 2017-06-07 12:37:23
Also in:
lkml
Hi Eric, I'll try very much to read this series tomorrow, can't do this today... On 06/06, Eric W. Biederman wrote:
quoted hunk ↗ jump to hunk
@@ -1380,13 +1380,6 @@ int do_prlimit(struct task_struct *tsk, unsigned int resource, return -EPERM; } - /* protect tsk->signal and tsk->sighand from disappearing */ - read_lock(&tasklist_lock); - if (!tsk->sighand) { - retval = -ESRCH; - goto out; - }
Yes, the comment is wrong. However we do need read_lock(tasklist_lock) to access ->group_leader. And the ->sighand != NULL check ensures that ->group_leader is the valid pointer. Also, update_rlimit_cpu() is not safe without tasklist / sighand-check. We can probably change this code to rely on rcu. Oleg.