In the Linux kernel, the following vulnerability has been resolved:
blk-iocost: use spin_lock_irqsave in adjust_inuse_and_calc_cost
adjust_inuse_and_calc_cost() use spin_lock_irq() and IRQ will be enabled when unlock. DEADLOCK might happen if we have held other locks and disabled IRQ before invoking it.
Fix it by using spin_lock_irqsave() instead, which can keep IRQ state consistent with before when unlock.
================================ WARNING: inconsistent lock state 5.10.0-02758-g8e5f91fd772f #26 Not tainted -------------------------------- inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage. kworker/2:3/388 [HC0[0]:SC0[0]:HE0:SE1] takes: ffff888118c00c28 (&bfqd->lock){?.-.}-{2:2}, at: spin_lock_irq ffff888118c00c28 (&bfqd->lock){?.-.}-{2:2}, at: bfq_bio_merge+0x141/0x390 {IN-HARDIRQ-W} state was registered at: __lock_acquire+0x3d7/0x1070 lock_acquire+0x197/0x4a0 __raw_spin_lock_irqsave _raw_spin_lock_irqsave+0x3b/0x60 bfq_idle_slice_timer_body bfq_idle_slice_timer+0x53/0x1d0 __run_hrtimer+0x477/0xa70 __hrtimer_run_queues+0x1c6/0x2d0 hrtimer_interrupt+0x302/0x9e0 local_apic_timer_interrupt __sysvec_apic_timer_interrupt+0xfd/0x420 run_sysvec_on_irqstack_cond sysvec_apic_timer_interrupt+0x46/0xa0 asm_sysvec_apic_timer_interrupt+0x12/0x20 irq event stamp: 837522 hardirqs last enabled at (837521): [] __raw_spin_unlock_irqrestore hardirqs last enabled at (837521): [] _raw_spin_unlock_irqrestore+0x3d/0x40 hardirqs last disabled at (837522): [] __raw_spin_lock_irq hardirqs last disabled at (837522): [] _raw_spin_lock_irq+0x43/0x50 softirqs last enabled at (835852): [] __do_softirq+0x558/0x8ec softirqs last disabled at (835845): [] asm_call_irq_on_stack+0xf/0x20
other info that might help us debug this: Possible unsafe locking scenario:
CPU0 ---- lock(&bfqd->lock); lock(&bfqd->lock);
* DEADLOCK *
3 locks held by kworker/2:3/388: #0: ffff888107af0f38 ((wq_completion)kthrotld){+.+.}-{0:0}, at: process_one_work+0x742/0x13f0 #1: ffff8881176bfdd8 ((work_completion)(&td->dispatch_work)){+.+.}-{0:0}, at: process_one_work+0x777/0x13f0 #2: ffff888118c00c28 (&bfqd->lock){?.-.}-{2:2}, at: spin_lock_irq #2: ffff888118c00c28 (&bfqd->lock){?.-.}-{2:2}, at: bfq_bio_merge+0x141/0x390
stack backtrace: CPU: 2 PID: 388 Comm: kworker/2:3 Not tainted 5.10.0-02758-g8e5f91fd772f #26 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 Workqueue: kthrotld blk_throtl_dispatch_work_fn Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x107/0x167 print_usage_bug valid_state mark_lock_irq.cold+0x32/0x3a mark_lock+0x693/0xbc0 mark_held_locks+0x9e/0xe0 __trace_hardirqs_on_caller lockdep_hardirqs_on_prepare.part.0+0x151/0x360 trace_hardirqs_on+0x5b/0x180 __raw_spin_unlock_irq _raw_spin_unlock_irq+0x24/0x40 spin_unlock_irq adjust_inuse_and_calc_cost+0x4fb/0x970 ioc_rqos_merge+0x277/0x740 __rq_qos_merge+0x62/0xb0 rq_qos_merge bio_attempt_back_merge+0x12c/0x4a0 blk_mq_sched_try_merge+0x1b6/0x4d0 bfq_bio_merge+0x24a/0x390 __blk_mq_sched_bio_merge+0xa6/0x460 blk_mq_sched_bio_merge blk_mq_submit_bio+0x2e7/0x1ee0 __submit_bio_noacct_mq+0x175/0x3b0 submit_bio_noacct+0x1fb/0x270 blk_throtl_dispatch_work_fn+0x1ef/0x2b0 process_one_work+0x83e/0x13f0 process_scheduled_works worker_thread+0x7e3/0xd80 kthread+0x353/0x470 ret_from_fork+0x1f/0x30