diff options
| author | Mike Galbraith <efault@gmx.de> | 2010-12-16 15:09:52 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-01-04 15:10:34 +0100 |
| commit | 4f8219875a0dad2cfad9e93a3fafcd9626db98d2 (patch) | |
| tree | 050e09c752c2b0f6045f85247c64890cf5d4ec48 | |
| parent | 6706125e291bd3dddd269e043323a6ab93ccd5fb (diff) | |
sched, autogroup: Fix potential access to freed memory
Oleg pointed out that the /proc interface kref_get() useage may race with
the final put during autogroup_move_group(). A signal->autogroup assignment
may be in flight when the /proc interface dereference, leaving them taking
a reference to an already dead group.
Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1292508592.5940.28.camel@maggy.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | kernel/sched_autogroup.c | 25 |
1 files changed, 17 insertions, 8 deletions
diff --git a/kernel/sched_autogroup.c b/kernel/sched_autogroup.c index 57a7ac286a0..c80fedcd476 100644 --- a/kernel/sched_autogroup.c +++ b/kernel/sched_autogroup.c @@ -41,6 +41,20 @@ static inline struct autogroup *autogroup_kref_get(struct autogroup *ag) return ag; } +static inline struct autogroup *autogroup_task_get(struct task_struct *p) +{ + struct autogroup *ag; + unsigned long flags; + + if (!lock_task_sighand(p, &flags)) + return autogroup_kref_get(&autogroup_default); + + ag = autogroup_kref_get(p->signal->autogroup); + unlock_task_sighand(p, &flags); + + return ag; +} + static inline struct autogroup *autogroup_create(void) { struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL); @@ -149,11 +163,7 @@ EXPORT_SYMBOL(sched_autogroup_detach); void sched_autogroup_fork(struct signal_struct *sig) { - struct task_struct *p = current; - - spin_lock_irq(&p->sighand->siglock); - sig->autogroup = autogroup_kref_get(p->signal->autogroup); - spin_unlock_irq(&p->sighand->siglock); + sig->autogroup = autogroup_task_get(current); } void sched_autogroup_exit(struct signal_struct *sig) @@ -172,7 +182,6 @@ __setup("noautogroup", setup_autogroup); #ifdef CONFIG_PROC_FS -/* Called with siglock held. */ int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice) { static unsigned long next = INITIAL_JIFFIES; @@ -194,7 +203,7 @@ int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice) return -EAGAIN; next = HZ / 10 + jiffies; - ag = autogroup_kref_get(p->signal->autogroup); + ag = autogroup_task_get(p); down_write(&ag->lock); err = sched_group_set_shares(ag->tg, prio_to_weight[*nice + 20]); @@ -209,7 +218,7 @@ int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice) void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m) { - struct autogroup *ag = autogroup_kref_get(p->signal->autogroup); + struct autogroup *ag = autogroup_task_get(p); down_read(&ag->lock); seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice); |