linux-kernel - Re: [PATCH v3 18/18] nvme-fc: do not reference lsrsp after failure

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Message-ID: <e4d7f84a-dd29-4b7a-a831-a8555125bf43@suse.de>
Date: Tue, 18 Mar 2025 12:33:22 +0100
From: Hannes Reinecke <hare@...e.de>
To: Daniel Wagner <wagi@...nel.org>, James Smart <james.smart@...adcom.com>,
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
 Chaitanya Kulkarni <kch@...dia.com>
Cc: Keith Busch <kbusch@...nel.org>, linux-nvme@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 18/18] nvme-fc: do not reference lsrsp after failure

On 3/18/25 11:40, Daniel Wagner wrote:
> The lsrsp object is maintained by the LLDD. The lifetime of the lsrsp
> object is implicit. Because there is no explicit cleanup/free call into
> the LLDD, it is not safe to assume after xml_rsp_fails, that the lsrsp
> is still valid. The LLDD could have freed the object already.
> 
> With the recent changes how fcloop tracks the resources, this is the
> case. Thus don't access lsrsp after xml_rsp_fails.
> 
> Signed-off-by: Daniel Wagner <wagi@...nel.org>
> ---
>   drivers/nvme/host/fc.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
> index b9929a5a7f4e3f3a03953379aceb90f0c1a0b561..2c32ba9ee688d7a683bbbf8fc57a5f9b32b2ab8d 100644
> --- a/drivers/nvme/host/fc.c
> +++ b/drivers/nvme/host/fc.c
> @@ -1410,9 +1410,8 @@ nvme_fc_xmt_disconnect_assoc(struct nvme_fc_ctrl *ctrl)
>   }
>   
>   static void
> -nvme_fc_xmt_ls_rsp_done(struct nvmefc_ls_rsp *lsrsp)
> +nvme_fc_xmt_ls_rsp_free(struct nvmefc_ls_rcv_op *lsop)
>   {
> -	struct nvmefc_ls_rcv_op *lsop = lsrsp->nvme_fc_private;
>   	struct nvme_fc_rport *rport = lsop->rport;
>   	struct nvme_fc_lport *lport = rport->lport;
>   	unsigned long flags;
> @@ -1433,6 +1432,14 @@ nvme_fc_xmt_ls_rsp_done(struct nvmefc_ls_rsp *lsrsp)
>   	nvme_fc_rport_put(rport);
>   }
>   
> +static void
> +nvme_fc_xmt_ls_rsp_done(struct nvmefc_ls_rsp *lsrsp)
> +{
> +	struct nvmefc_ls_rcv_op *lsop = lsrsp->nvme_fc_private;
> +
> +	nvme_fc_xmt_ls_rsp_free(lsop);
> +}
> +
>   static void
>   nvme_fc_xmt_ls_rsp(struct nvmefc_ls_rcv_op *lsop)
>   {
> @@ -1450,7 +1457,7 @@ nvme_fc_xmt_ls_rsp(struct nvmefc_ls_rcv_op *lsop)
>   		dev_warn(lport->dev,
>   			"LLDD rejected LS RSP xmt: LS %d status %d\n",
>   			w0->ls_cmd, ret);
> -		nvme_fc_xmt_ls_rsp_done(lsop->lsrsp);
> +		nvme_fc_xmt_ls_rsp_free(lsop);
>   		return;
>   	}
>   }
> 
Hmm. That is a weird change. 'lsop->lsrsp' clearly _was_ valid just before:

         ret = lport->ops->xmt_ls_rsp(&lport->localport, &rport->remoteport,
                                      lsop->lsrsp);
         if (ret) {
                 dev_warn(lport->dev,
                         "LLDD rejected LS RSP xmt: LS %d status %d\n",
                         w0->ls_cmd, ret);
                 nvme_fc_xmt_ls_rsp_done(lsop->lsrsp);
                 return;
         }

so ->xmt_ls_rsp() would have invalidated one of the arguments.
Plus 'nvme_fc_xmt_ls_rsp_done()' is now a wrapper around
'nvme_fc_xmt_ls_rsp_free()'.
So why not go the full length and kill nvme_fc_xmt_ls_rsp_done()
completely?
Hmm?

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich