linux-kernel - Re: [PATCH 18/26] target/iscsi: Allocate session IDs from an IDA

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Date:   Fri, 27 Jul 2018 12:38:14 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Mike Christie <mchristi@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        "Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
        Bart Van Assche <bart.vanassche@....com>,
        Hannes Reinecke <hare@...e.com>,
        Kees Cook <keescook@...omium.org>,
        Varun Prakash <varun@...lsio.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org
Subject: Re: [PATCH 18/26] target/iscsi: Allocate session IDs from an IDA

On Thu, Jul 26, 2018 at 12:13:49PM -0500, Mike Christie wrote:
> If we want to fix the bug first, then I made the attached patch and I
> can submit it.

How about I take it through my tree to minimise the amount of rebasing
I'll need to do?  I'm already dependent on the nvdimm tree and I'd rather
not depend on the scsi tree as well.  I'll queue it up in front of my
IDA change to maximise its backportability.

> >From 80c495c3d7f4487c1b6f52f70e8ddc74dcb70794 Mon Sep 17 00:00:00 2001
> From: Mike Christie <mchristi@...hat.com>
> Date: Thu, 26 Jul 2018 12:06:07 -0500
> Subject: [PATCH] iscsi target: fix session creation failure handling
> 
> The problem is that iscsi_login_zero_tsih_s1 sets conn->sess early in
> iscsi_login_set_conn_values. If the function fails later like when we
> alloc the idr it does kfree(sess) and leaves the conn->sess pointer set.
> iscsi_login_zero_tsih_s1 then returns -Exyz and we then call
> iscsi_target_login_sess_out and access the freed memory.
> 
> This patch has iscsi_login_zero_tsih_s1 either completely setup the
> session or completely tear it down, so later in
> iscsi_target_login_sess_out we can just check for it being set to the
> connection.
> ---
>  drivers/target/iscsi/iscsi_target_login.c | 35 ++++++++++++++++++-------------
>  1 file changed, 21 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
> index 9950178..e20d811 100644
> --- a/drivers/target/iscsi/iscsi_target_login.c
> +++ b/drivers/target/iscsi/iscsi_target_login.c
> @@ -348,8 +348,7 @@ static int iscsi_login_zero_tsih_s1(
>  		pr_err("idr_alloc() for sess_idr failed\n");
>  		iscsit_tx_login_rsp(conn, ISCSI_STATUS_CLS_TARGET_ERR,
>  				ISCSI_LOGIN_STATUS_NO_RESOURCES);
> -		kfree(sess);
> -		return -ENOMEM;
> +		goto free_sess;
>  	}
>  
>  	sess->creation_time = get_jiffies_64();
> @@ -365,20 +364,28 @@ static int iscsi_login_zero_tsih_s1(
>  				ISCSI_LOGIN_STATUS_NO_RESOURCES);
>  		pr_err("Unable to allocate memory for"
>  				" struct iscsi_sess_ops.\n");
> -		kfree(sess);
> -		return -ENOMEM;
> +		goto remove_idr;
>  	}
>  
>  	sess->se_sess = transport_init_session(TARGET_PROT_NORMAL);
>  	if (IS_ERR(sess->se_sess)) {
>  		iscsit_tx_login_rsp(conn, ISCSI_STATUS_CLS_TARGET_ERR,
>  				ISCSI_LOGIN_STATUS_NO_RESOURCES);
> -		kfree(sess->sess_ops);
> -		kfree(sess);
> -		return -ENOMEM;
> +		goto free_ops;
>  	}
>  
>  	return 0;
> +
> +free_ops:
> +	kfree(sess->sess_ops);
> +remove_idr:
> +	spin_lock_bh(&sess_idr_lock);
> +	idr_remove(&sess_idr, sess->session_index);
> +	spin_unlock_bh(&sess_idr_lock);
> +free_sess:
> +	kfree(sess);
> +	conn->sess = NULL;
> +	return -ENOMEM;
>  }
>  
>  static int iscsi_login_zero_tsih_s2(
> @@ -1161,13 +1168,13 @@ void iscsi_target_login_sess_out(struct iscsi_conn *conn,
>  				   ISCSI_LOGIN_STATUS_INIT_ERR);
>  	if (!zero_tsih || !conn->sess)
>  		goto old_sess_out;
> -	if (conn->sess->se_sess)
> -		transport_free_session(conn->sess->se_sess);
> -	if (conn->sess->session_index != 0) {
> -		spin_lock_bh(&sess_idr_lock);
> -		idr_remove(&sess_idr, conn->sess->session_index);
> -		spin_unlock_bh(&sess_idr_lock);
> -	}
> +
> +	transport_free_session(conn->sess->se_sess);
> +
> +	spin_lock_bh(&sess_idr_lock);
> +	idr_remove(&sess_idr, conn->sess->session_index);
> +	spin_unlock_bh(&sess_idr_lock);
> +
>  	kfree(conn->sess->sess_ops);
>  	kfree(conn->sess);
>  	conn->sess = NULL;
> -- 
> 1.8.3.1
>