linux-kernel - Re: [PATCH] scsi: target: cxgbit: check skb dequeue result

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Date:   Fri, 7 Apr 2023 21:16:18 +0200
From:   Bodo Stroesser <bostroesser@...il.com>
To:     Denis Plotnikov <den-plotnikov@...dex-team.ru>,
        linux-scsi@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, target-devel@...r.kernel.org,
        varun@...lsio.com, nab@...ux-iscsi.org, martin.petersen@...cle.com
Subject: Re: [PATCH] scsi: target: cxgbit: check skb dequeue result

On 06.04.23 17:04, Denis Plotnikov wrote:
> On a couple of abort packet paths skb dequeuing may end up with
> returning NULL, which, in turn, may end up with further null
> pointer dereference.
> 
> Fix it by checking the return value of skb dequeuing.
> 
> Found by Linux Verification Center(linuxtesting.org) with SVACE.
> 
> Fixes: 9730ffcb8957 (cxgbit: add files for cxgbit.ko)
> Signed-off-by: Denis Plotnikov <den-plotnikov@...dex-team.ru>
> ---
>   drivers/target/iscsi/cxgbit/cxgbit_cm.c | 10 +++++++---
>   1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/target/iscsi/cxgbit/cxgbit_cm.c b/drivers/target/iscsi/cxgbit/cxgbit_cm.c
> index 518ded214e74..d43fd761c20a 100644
> --- a/drivers/target/iscsi/cxgbit/cxgbit_cm.c
> +++ b/drivers/target/iscsi/cxgbit/cxgbit_cm.c
> @@ -669,6 +669,9 @@ static int cxgbit_send_abort_req(struct cxgbit_sock *csk)
>   		cxgbit_send_tx_flowc_wr(csk);
>   
>   	skb = __skb_dequeue(&csk->skbq);
> +	if (!skb)
> +		return 0;
> +
>   	cxgb_mk_abort_req(skb, len, csk->tid, csk->txq_idx,
>   			  csk->com.cdev, cxgbit_abort_arp_failure);
>   
> @@ -1769,9 +1772,10 @@ static void cxgbit_abort_req_rss(struct cxgbit_sock *csk, struct sk_buff *skb)
>   		cxgbit_send_tx_flowc_wr(csk);
>   
>   	rpl_skb = __skb_dequeue(&csk->skbq);
> -
> -	cxgb_mk_abort_rpl(rpl_skb, len, csk->tid, csk->txq_idx);
> -	cxgbit_ofld_send(csk->com.cdev, rpl_skb);
> +	if (!rpl_skb) {

Honestly I have no clue about cxgbit, but to avoid null pointer
dereference, shouldn't it be "if (rpl_skb) {"?

Bodo


> +		cxgb_mk_abort_rpl(rpl_skb, len, csk->tid, csk->txq_idx);
> +		cxgbit_ofld_send(csk->com.cdev, rpl_skb);
> +	}
>   
>   	if (wakeup_thread) {
>   		cxgbit_queue_rx_skb(csk, skb);