Re: [PATCH] scsi: libfc: Fix rport kref leak in fc_rport_enter_ready()

[Hannes Reinecke <hare@suse.de>]

On 11/8/26 10:01 AM, Weidong Wang via B4 Relay wrote:
> From: Weidong Wang <weidongw@illinois.edu>
> 
> fc_rport_enter_ready() takes a reference on the rport unconditionally,
> but only queues event_work, whose handler drops that reference, when no
> event is pending. If rdata->event is already set, the && short-circuits
> past both queue_work() and the compensating kref_put(), so the reference
> is leaked and the fc_rport_priv is never freed.
> 
> This is reachable from the wire: a PLOGI from a well-known address goes
> straight to fc_rport_enter_ready(), and a second PLOGI for the same
> S_ID while RPORT_EV_READY is still pending enters it again. After the
> rport is logged out, kmemleak reports:
> 
>    unreferenced object 0xffff888... (size 512):
>    backtrace:
>      __kmalloc_noprof
>      fc_rport_create
>      fc_rport_recv_req
>      fc_lport_recv_els_req
>      fc_lport_recv
>      fcoe_receive_work
> 
> Commit 823a65409c89 ("scsi: libfc: Skip additional kref updating work
> event") fixed the same pattern in fc_rport_enter_delete(). Do the same
> here: only take the reference when no event is pending, i.e. when the
> work is actually going to be queued.
> 
> The issue was found with an LLM-based bug-finding tool; the reproducer,
> fix and changelog were drafted with AI assistance (Claude), then
> reviewed and tested by the submitter.
> 
> Fixes: 4d2095cc42a2 ("scsi: libfc: Revisit kref handling")
> Cc: stable@vger.kernel.org
> Signed-off-by: Weidong Wang <weidongw@illinois.edu>
> ---
> Tested on v7.4-rc1 (05441d697f7f), x86_64, KASAN + kmemleak, QEMU/KVM.
> Reproducer: software FCoE instance on lo; raw FCoE ELS frames injected
> with AF_PACKET (PLOGI from well-known S_IDs 0xfffc01.., a second PLOGI
> for the same S_ID while RPORT_EV_READY is pending, then LOGO), 120 rports.
> 
>                     2nd enter_ready with    kmemleak unreferenced
>                     event pending           fc_rport_priv (512 B)
>    unpatched        116                     99
>    patched          104                     0
> 
> READY/delete work events are processed the same with and without the
> patch; no KASAN/UBSAN/WARN splats. checkpatch clean, no new W=1 warnings.
> The reproducer can be shared on request.
> ---
>   drivers/scsi/libfc/fc_rport.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/scsi/libfc/fc_rport.c b/drivers/scsi/libfc/fc_rport.c
> index c25979d96..7b0938544 100644
> --- a/drivers/scsi/libfc/fc_rport.c
> +++ b/drivers/scsi/libfc/fc_rport.c
> @@ -550,10 +550,11 @@ static void fc_rport_enter_ready(struct fc_rport_priv *rdata)
>   
>   	FC_RPORT_DBG(rdata, "Port is Ready\n");
>   
> -	kref_get(&rdata->kref);
> -	if (rdata->event == RPORT_EV_NONE &&
> -	    !queue_work(rport_event_queue, &rdata->event_work))
> -		kref_put(&rdata->kref, fc_rport_destroy);
> +	if (rdata->event == RPORT_EV_NONE) {
> +		kref_get(&rdata->kref);
> +		if (!queue_work(rport_event_queue, &rdata->event_work))
> +			kref_put(&rdata->kref, fc_rport_destroy);
> +	}
>   
>   	rdata->event = RPORT_EV_READY;
>   }
> 
> ---
> base-commit: 05441d697f7f9a927264f4058cbbc6a03dfcac9d
> change-id: 20261108-h123-send-723aeb555069
> 
> Best regards,
> --
> Weidong Wang <weidongw@illinois.edu>
> 
> 
Reviewed-by: Hannes Reinecke <hare@kernel.org>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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