Oleg Nesterov <[email protected]> writes: > 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.
As of 4.12-rc1 The code does not access group_leader anymore. > Also, update_rlimit_cpu() is not safe without tasklist / sighand-check. > > We can probably change this code to rely on rcu. Good point a NULL sighand will cause update_rlimit_cpu to OOPS. Grr. There is a point in my tree where this is perfectly safe. But not at this point. Consider this patch dropped for the moment. Eric
