| Date | Wed, 7 Jun 2017 14:36:57 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 06/26] rlimit: Remove unnecessary grab of tasklist_lock |
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Hi Eric,
I'll try very much to read this series tomorrow, can't do this today...
On 06/06, Eric W. Biederman wrote: > > @@ -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.
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