CC Oleg On 07/13/2015, 12:51 AM, 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 --- drivers/tty/n_tty.c | 15 ++++++++++++--- drivers/tty/tty_io.c | 17 ++++++++++++----- 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index c9c27f6..de67b2c 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -2137,6 +2137,8 @@ extern ssize_t redirected_tty_write(struct file *, const char __user *,

static int job_control(struct tty_struct *tty, struct file *file) { + struct pid *pgrp; + /* Job control check -- must be done at start and after every sleep (POSIX.1 7.1.1.4). */ /* NOTE: not yet done after every sleep pending a thorough @@ -2146,18 +2148,25 @@ static int job_control(struct tty_struct *tty, struct file *file) current->signal->tty != tty) return 0;

+ rcu_read_lock(); + pgrp = task_pgrp(current); + spin_lock_irq(&tty->ctrl_lock); if (!tty->pgrp) printk(KERN_ERR "n_tty_read: no tty->pgrp!\n"); - else if (task_pgrp(current) != tty->pgrp) { + else if (pgrp != tty->pgrp) { spin_unlock_irq(&tty->ctrl_lock); - if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned()) + if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned()) { + rcu_read_unlock(); return -EIO; - kill_pgrp(task_pgrp(current), SIGTTIN, 1); + } + kill_pgrp(pgrp, SIGTTIN, 1); + rcu_read_unlock(); set_thread_flag(TIF_SIGPENDING); return -ERESTARTSYS; } spin_unlock_irq(&tty->ctrl_lock); + rcu_read_unlock(); return 0; }

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 57fc6ee..6bdfb98 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -388,33 +388,40 @@ 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;

+ 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; } - if (task_pgrp(current) == tty->pgrp) + if (pgrp == tty->pgrp) goto out_unlock; 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: spin_unlock_irqrestore(&tty->ctrl_lock, flags); +out_rcuunlock: + rcu_read_unlock(); return ret; }

thanks, -- js suse labs -- To unsubscribe, e-mail: opensuse-kernel+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-kernel+owner@opensuse.org