| Message ID | 1325618059-20113-2-git-send-email-apw@canonical.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Jan 03, 2012 at 07:14:19PM +0000, Andy Whitcroft wrote: > From: Mike Galbraith <efault@gmx.de> > > commit f26f9aff6aaf67e9a430d16c266f91b13a5bff64 upstream. > > idle_balance() drops/retakes rq->lock, leaving the previous task > vulnerable to set_tsk_need_resched(). Clear it after we return > from balancing instead, and in setup_thread_stack() as well, so > no successfully descheduled or never scheduled task has it set. > > Need resched confused the skip_clock_update logic, which assumes > that the next call to update_rq_clock() will come nearly immediately > after being set. Make the optimization robust against the waking > a sleeper before it sucessfully deschedules case by checking that > the current task has not been dequeued before setting the flag, > since it is that useless clock update we're trying to save, and > clear unconditionally in schedule() proper instead of conditionally > in put_prev_task(). > > Signed-off-by: Mike Galbraith <efault@gmx.de> > Signed-off-by: Andi Kleen <ak@linux.intel.com> > Reported-by: Bjoern B. Brandenburg <bbb.lst@gmail.com> > Tested-by: Yong Zhang <yong.zhang0@gmail.com> > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > LKML-Reference: <1291802742.1417.9.camel@marge.simson.net> > Signed-off-by: Ingo Molnar <mingo@elte.hu> > Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> > Signed-off-by: Brad Figg <brad.figg@canonical.com> > > CVE-2011-4621 > BugLink: http://bugs.launchpad.net/bugs/911401 > Signed-off-by: Andy Whitcroft <apw@canonical.com> > --- > kernel/fork.c | 1 + > kernel/sched.c | 6 +++--- > 2 files changed, 4 insertions(+), 3 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 49ffdad..1819195 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -273,6 +273,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig) > > setup_thread_stack(tsk, orig); > clear_user_return_notifier(tsk); > + clear_tsk_need_resched(tsk); > stackend = end_of_stack(tsk); > *stackend = STACK_END_MAGIC; /* for overflow detection */ > > diff --git a/kernel/sched.c b/kernel/sched.c > index 63b4a14..87e47d0 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -564,7 +564,7 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) > * A queue event has occurred, and we're going to schedule. In > * this case, we can save a useless back to back clock update. > */ > - if (test_tsk_need_resched(p)) > + if (rq->curr->se.on_rq && test_tsk_need_resched(rq->curr)) > rq->skip_clock_update = 1; > } > > @@ -3536,7 +3536,6 @@ static void put_prev_task(struct rq *rq, struct task_struct *prev) > { > if (prev->se.on_rq) > update_rq_clock(rq); > - rq->skip_clock_update = 0; > prev->sched_class->put_prev_task(rq, prev); > } > > @@ -3599,7 +3598,6 @@ need_resched_nonpreemptible: > hrtick_clear(rq); > > raw_spin_lock_irq(&rq->lock); > - clear_tsk_need_resched(prev); > > if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) { > if (unlikely(signal_pending_state(prev->state, prev))) > @@ -3616,6 +3614,8 @@ need_resched_nonpreemptible: > > put_prev_task(rq, prev); > next = pick_next_task(rq); > + clear_tsk_need_resched(prev); > + rq->skip_clock_update = 0; > > if (likely(prev != next)) { > sched_info_switch(prev, next); > -- > 1.7.5.4 > > > -- > kernel-team mailing list > kernel-team@lists.ubuntu.com > https://lists.ubuntu.com/mailman/listinfo/kernel-team >
diff --git a/kernel/fork.c b/kernel/fork.c index 49ffdad..1819195 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -273,6 +273,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig) setup_thread_stack(tsk, orig); clear_user_return_notifier(tsk); + clear_tsk_need_resched(tsk); stackend = end_of_stack(tsk); *stackend = STACK_END_MAGIC; /* for overflow detection */ diff --git a/kernel/sched.c b/kernel/sched.c index 63b4a14..87e47d0 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -564,7 +564,7 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) * A queue event has occurred, and we're going to schedule. In * this case, we can save a useless back to back clock update. */ - if (test_tsk_need_resched(p)) + if (rq->curr->se.on_rq && test_tsk_need_resched(rq->curr)) rq->skip_clock_update = 1; } @@ -3536,7 +3536,6 @@ static void put_prev_task(struct rq *rq, struct task_struct *prev) { if (prev->se.on_rq) update_rq_clock(rq); - rq->skip_clock_update = 0; prev->sched_class->put_prev_task(rq, prev); } @@ -3599,7 +3598,6 @@ need_resched_nonpreemptible: hrtick_clear(rq); raw_spin_lock_irq(&rq->lock); - clear_tsk_need_resched(prev); if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) { if (unlikely(signal_pending_state(prev->state, prev))) @@ -3616,6 +3614,8 @@ need_resched_nonpreemptible: put_prev_task(rq, prev); next = pick_next_task(rq); + clear_tsk_need_resched(prev); + rq->skip_clock_update = 0; if (likely(prev != next)) { sched_info_switch(prev, next);