From: Tianchen Ding <dtcccc@linux.alibaba.com> mainline inclusion from mainline-v6.18-rc1 commit 5d808c78d97251af1d3a3e4f253e7d6c39fd871e category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/ID8CE7 CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- We met a SCHED_WARN in set_next_buddy(): __warn_printk set_next_buddy yield_to_task_fair yield_to kvm_vcpu_yield_to [kvm] ... After a short dig, we found the rq_lock held by yield_to() may not be exactly the rq that the target task belongs to. There is a race window against try_to_wake_up(). CPU0 target_task blocking on CPU1 lock rq0 & rq1 double check task_rq == p_rq, ok woken to CPU2 (lock task_pi & rq2) task_rq = rq2 yield_to_task_fair (w/o lock rq2) In this race window, yield_to() is operating the task w/o the correct lock. Fix this by taking task pi_lock first. Fixes: d95f41220065 ("sched: Add yield_to(task, preempt) functionality") Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20241231055020.6521-1-dtcccc@linux.alibaba.com Conflicts: kernel/sched/syscalls.c kernel/sched/core.c [Context differences.] Signed-off-by: Xia Fukun <xiafukun@huawei.com> --- kernel/sched/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5d2937935b47..a7af86e1234c 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7372,7 +7372,7 @@ int __sched yield_to(struct task_struct *p, bool preempt) unsigned long flags; int yielded = 0; - local_irq_save(flags); + raw_spin_lock_irqsave(&p->pi_lock, flags); rq = this_rq(); again: @@ -7415,7 +7415,7 @@ int __sched yield_to(struct task_struct *p, bool preempt) out_unlock: double_rq_unlock(rq, p_rq); out_irq: - local_irq_restore(flags); + raw_spin_unlock_irqrestore(&p->pi_lock, flags); if (yielded > 0) schedule(); -- 2.34.1