Messages in this thread | | | Date | Sun, 28 Jun 2015 15:27:26 -0400 | From | Peter Hurley <> | Subject | Re: [PATCH v2 1/2] tty: add missing rcu_read_lock for task_pgrp |
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Hi Patrick,
On 06/27/2015 08:51 PM, Patrick Donnelly wrote: > task_pgrp requires an rcu or tasklist lock to be obtained if the returned pid > is to be dereferenced, which kill_pgrp does. Obtain an RCU lock for the > duration of use. > > Signed-off-by: Patrick Donnelly <batrick@batbytes.com> > --- > drivers/tty/tty_io.c | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c > index 57fc6ee..fbb55db 100644 > --- a/drivers/tty/tty_io.c > +++ b/drivers/tty/tty_io.c > @@ -388,33 +388,39 @@ EXPORT_SYMBOL_GPL(tty_find_polling_driver); > int tty_check_change(struct tty_struct *tty) > { > unsigned long flags; > + struct pid *pgrp; > int ret = 0; > > if (current->signal->tty != tty) > return 0; > > - spin_lock_irqsave(&tty->ctrl_lock, flags); > + rcu_read_lock(); > + pgrp = task_pgrp(current); > > + spin_lock_irqsave(&tty->ctrl_lock, flags); > if (!tty->pgrp) { > printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n"); > - goto out_unlock; > + goto out_irqunlock;
The label name changing is not really necessary and would reduce diff count. It would be nice to get the printk() out from the locks as well (in a follow-on patch?)
Regards, Peter Hurley
> } > - if (task_pgrp(current) == tty->pgrp) > - goto out_unlock; > + if (pgrp == tty->pgrp) > + goto out_irqunlock; > spin_unlock_irqrestore(&tty->ctrl_lock, flags); > + > if (is_ignored(SIGTTOU)) > - goto out; > + goto out_rcuunlock; > if (is_current_pgrp_orphaned()) { > ret = -EIO; > - goto out; > + goto out_rcuunlock; > } > - kill_pgrp(task_pgrp(current), SIGTTOU, 1); > + kill_pgrp(pgrp, SIGTTOU, 1); > + rcu_read_unlock(); > set_thread_flag(TIF_SIGPENDING); > ret = -ERESTARTSYS; > -out: > return ret; > -out_unlock: > +out_irqunlock: > spin_unlock_irqrestore(&tty->ctrl_lock, flags); > +out_rcuunlock: > + rcu_read_unlock(); > return ret; > } > >
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