linux-kernel - Re: [PATCH] nvme-fc: fix sleep-in-atomic-context bug caused by nvme_fc_rcv_ls

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Date:   Tue, 4 Oct 2022 19:10:19 +0800 (GMT+08:00)
From:   duoming@....edu.cn
To:     "James Smart" <jsmart2021@...il.com>
Cc:     linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
        james.smart@...adcom.com, kbusch@...nel.org, axboe@...com,
        hch@....de, sagi@...mberg.me
Subject: Re: [PATCH] nvme-fc: fix sleep-in-atomic-context bug caused by
 nvme_fc_rcv_ls_req

Hello,

On Mon, 3 Oct 2022 10:48:31 -0700 James Smart wrote:

> On 10/2/2022 7:56 PM, James Smart wrote:
> > On 10/2/2022 6:50 PM, duoming@....edu.cn wrote:
> >> Hello,
> >>
> >> On Sun, 2 Oct 2022 10:12:15 -0700 James Smart wrote:
> >>
> >>> On 10/1/2022 5:19 PM, Duoming Zhou wrote:
> >>>> The function lpfc_poll_timeout() is a timer handler that runs in an
> >>>> atomic context, but it calls "kzalloc(.., GFP_KERNEL)" that may sleep.
> >>>> As a result, the sleep-in-atomic-context bug will happen. The processes
> >>>> is shown below:
> >>>>
> >>>> lpfc_poll_timeout()
> >>>>    lpfc_sli_handle_fast_ring_event()
> >>>>     lpfc_sli_process_unsol_iocb()
> >>>>      lpfc_complete_unsol_iocb()
> >>>>       lpfc_nvme_unsol_ls_handler()
> >>>>        lpfc_nvme_handle_lsreq()
> >>>>         nvme_fc_rcv_ls_req()
> >>>>          kzalloc(sizeof(.., GFP_KERNEL) //may sleep
> >>>>
> >>>> This patch changes the gfp_t parameter of kzalloc() from GFP_KERNEL to
> >>>> GFP_ATOMIC in order to mitigate the bug.
> >>>>
> >>>> Fixes: 14fd1e98afaf ("nvme-fc: Add Disconnect Association Rcv support")
> >>>> Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> >>>> ---
> >>>>    drivers/nvme/host/fc.c | 2 +-
> >>>>    1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> >>>> index 127abaf9ba5..36698dfc8b3 100644
> >>>> --- a/drivers/nvme/host/fc.c
> >>>> +++ b/drivers/nvme/host/fc.c
> >>>> @@ -1754,7 +1754,7 @@ nvme_fc_rcv_ls_req(struct nvme_fc_remote_port 
> >>>> *portptr,
> >>>>        lsop = kzalloc(sizeof(*lsop) +
> >>>>                sizeof(union nvmefc_ls_requests) +
> >>>>                sizeof(union nvmefc_ls_responses),
> >>>> -            GFP_KERNEL);
> >>>> +            GFP_ATOMIC);
> >>>>        if (!lsop) {
> >>>>            dev_info(lport->dev,
> >>>>                "RCV %s LS failed: No memory\n",
> >>>
> >>> I would prefer this was fixed within lpfc rather than introducing atomic
> >>> allocations (1st in either host or target transport).  It was introduced
> >>> by lpfc change in irq handling style.
> >>
> >> Thank your for your reply and suggestions!
> >>
> >> Do you think change the lpfc_poll_timeout() to a delayed_work is better?
> >>
> >> Best regards,
> >> Duoming Zhou
> > 
> > as a minimum: the lpfc_complete_unsol_iocb handler should be passing off 
> > the iocb to a work queue routine - so that the context changes so that 
> > either nvme host or nvmet ls callback routines can be called. If 
> > possible, it should do the axchg alloc - to avoid a GFP_ATOMIC there as 
> > well...
> > 
> > It's usually best for these nvme LS's and ELS's to be done in a slow 
> > path thread/work queue element. That may mean segmenting a little 
> > earlier in the path.
> > 
> > -- james
> > 
> 
> looking further...   lpfc_poll_timeout() should only be used on an SLI-3 
> adapter.  The existing SLI-3 adapters don't support NVMe. So I'm a 
> little confused by this stack trace.

I found this problem through a static analysis tool wroten by myself.
I think the hacker may simulate the hardware to trigger this stack trace.
So, I send the patch to correct the problem.

> Can you describe what the system config/software setup is and 
> specifically what lpfc adapter is being used (dmesg attachment logs are 
> sufficient, or lspci output).

Best regards,
Duoming Zhou