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

[Denis Plotnikov]

On 07.04.2023 22:16, Bodo Stroesser wrote:
> 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@xxxxxxxxxxxxxx>
> > ---
> >   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) {"?

Yes it should. Thanks for finding that. I'll resend the patch.

Frankly, I have no clue about cxgbit as well, so may be there is a 
better way to cope with the null pointer issue here.

Denis

> 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);