linux-kernel - Re: [PATCH v2 2/2] libiscsi: disallow binding an already-bound connection

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Date: Fri, 24 May 2024 11:14:07 -0500
From: Mike Christie <michael.christie@...cle.com>
To: Khazhismel Kumykov <khazhy@...omium.org>, Lee Duncan <lduncan@...e.com>,
        Chris Leech <cleech@...hat.com>
Cc: "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        open-iscsi@...glegroups.com, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, Khazhismel Kumykov <khazhy@...gle.com>
Subject: Re: [PATCH v2 2/2] libiscsi: disallow binding an already-bound
 connection

On 5/23/24 5:21 PM, Khazhismel Kumykov wrote:
> This fixes issue where misbehaving userspace initiator could bind the
> same connection multiple times, which would leak the old connection
> socket without cleaning it up.
> 
> For iscsi_tcp, it calls iscsi_suspend_tx directly in stop_conn. Update
> this to iscsi_conn_unbind, which matches the lifecycle of other drivers,
> and clears the CONN_FLAG_BOUND.
> 
> Suggested-by: Mike Christie <michael.christie@...cle.com>
> Signed-off-by: Khazhismel Kumykov <khazhy@...gle.com>
> ---
>  drivers/scsi/iscsi_tcp.c | 2 +-
>  drivers/scsi/libiscsi.c  | 6 ++++++
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
> index deb9252e02e6..1d93404515ae 100644
> --- a/drivers/scsi/iscsi_tcp.c
> +++ b/drivers/scsi/iscsi_tcp.c
> @@ -696,7 +696,7 @@ static void iscsi_sw_tcp_conn_stop(struct iscsi_cls_conn *cls_conn, int flag)
>  	wake_up_interruptible(sk_sleep(sock->sk));
>  
>  	/* stop xmit side */
> -	iscsi_suspend_tx(conn);
> +	iscsi_conn_unbind(cls_conn, true);
>  
>  	/* stop recv side and release socket */
>  	iscsi_sw_tcp_release_conn(conn);
> diff --git a/drivers/scsi/libiscsi.c b/drivers/scsi/libiscsi.c
> index 0fda8905eabd..0fb98eb53584 100644
> --- a/drivers/scsi/libiscsi.c
> +++ b/drivers/scsi/libiscsi.c
> @@ -3453,6 +3453,12 @@ int iscsi_conn_bind(struct iscsi_cls_session *cls_session,
>  	struct iscsi_conn *conn = cls_conn->dd_data;
>  
>  	spin_lock_bh(&session->frwd_lock);
> +	if (test_bit(ISCSI_CONN_FLAG_BOUND, &conn->flags)) {
> +		spin_unlock_bh(&session->frwd_lock);
> +		return -EBUSY;
> +	}
> +

If some of the driver's bind_conn callout fails then it could leave the
ISCSI_CONN_FLAG_BOUND bit set, and this will fail on a retry.

It's ok to call iscsi_conn_bind at the end of the bind_conn callout
like how iscsi_tcp and cxgbi* do. So for iscsi_iser.c, be_iscsi.c,
bnx2i_iscsi.c, and qedi_iscsi.c you need to move their iscsi_conn_bind
to the end of their bind_conn callout.

You could also keep the the existing flow but add unwind/goto error
handling to those drivers, but I think just moving the iscsi_conn_bind
call to the end of the function is easier and it syncs all the drivers
behavior which is nice.