Re: [PATCH RESEND] scsi: fcoe: Fix potential deadlock on &fip->ctlr_lock

[Davidlohr Bueso]

On Wed, 16 Aug 2023, Chengfeng Ye wrote:

> There is a long call chain that &fip->ctlr_lock is acquired by isr
> fnic_isr_msix_wq_copy() under hard irq context. Thus other process
> context code acquiring the lock should disable irq, otherwise
> deadlock could happen if the irq preempt the execution while the
> lock is held in process context on the same CPU.
>
> [ISR]
> fnic_isr_msix_wq_copy()
> -> fnic_wq_copy_cmpl_handler()
> -> fnic_fcpio_cmpl_handler()
> -> fnic_fcpio_flogi_reg_cmpl_handler()
> -> fnic_flush_tx()
> -> fnic_send_frame()
> -> fcoe_ctlr_els_send()
> -> spin_lock_bh(&fip->ctlr_lock)
>
> [Process Context]
> 1. fcoe_ctlr_timer_work()
> -> fcoe_ctlr_flogi_send()
> -> spin_lock_bh(&fip->ctlr_lock)
>
> 2. fcoe_ctlr_recv_work()
> -> fcoe_ctlr_recv_handler()
> -> fcoe_ctlr_recv_els()
> -> fcoe_ctlr_announce()
> -> spin_lock_bh(&fip->ctlr_lock)
>
> 3. fcoe_ctlr_recv_work()
> -> fcoe_ctlr_recv_handler()
> -> fcoe_ctlr_recv_els()
> -> fcoe_ctlr_flogi_retry()
> -> spin_lock_bh(&fip->ctlr_lock)
>
> 4. -> fcoe_xmit()
> -> fcoe_ctlr_els_send()
> -> spin_lock_bh(&fip->ctlr_lock)
>
> spin_lock_bh() is not enough since fnic_isr_msix_wq_copy() is a
> hardirq.
>
> These flaws were found by an experimental static analysis tool I am
> developing for irq-related deadlock.
>
> The patch fix the potential deadlocks by spin_lock_irqsave() to
> disable hard irq.

Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>