linux-kernel - Re: [PATCH v2] RDMA: release allocated skb

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Message-ID: <CAEkB2ERA_Tn_yYz=ZQ58rF6sLGopxFghuTFBD=pWwcPwjLjTmw@mail.gmail.com>
Date:   Fri, 4 Oct 2019 13:12:55 -0500
From:   Navid Emamdoost <navid.emamdoost@...il.com>
To:     Potnuri Bharat Teja <bharat@...lsio.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>,
        Navid Emamdoost <emamd001@....edu>,
        Stephen McCamant <smccaman@....edu>, Kangjie Lu <kjlu@....edu>,
        Doug Ledford <dledford@...hat.com>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] RDMA: release allocated skb

Hi Leon and Potnuri,

Based on the following call sequence, skb is passed along to uld_send().
c4iw_ref_send_wait
        c4iw_ofld_send
                cxgb4_ofld_send
                        t4_ofld_send
                                uld_send

In uld_send() skb is consumed (released or added to queue) via
ctrl_xmit() or ofld_xmit(), which assures no leak is happening. But in
the condition check for txq_info the return value is NET_XMIT_DROP
which means the skb should be released. Here I believe skb is being
leaked:

        txq_info = adap->sge.uld_txq_info[tx_uld_type];
        if (unlikely(!txq_info)) {
                WARN_ON(true);
                return NET_XMIT_DROP;
        }

Please let me know what you think, then I can go ahead and fix the patch.

Thank you,
Navid.

On Thu, Oct 3, 2019 at 5:25 AM Potnuri Bharat Teja <bharat@...lsio.com> wrote:
>
> On Thursday, October 10/03/19, 2019 at 03:05:06 +0530, Navid Emamdoost wrote:
> > Hi Jason,
> >
> > Thanks for the feedback. Yes, you are right if the skb release is
> > moved under err4 label it will cause a double free as
> > c4iw_ref_send_wait will release skb in case of error.
> > So, in order to avoid leaking skb in case of c4iw_bar2_addrs failure,
> > the kfree(skb) could be placed under the error check like the way
> > patch v1 did. Do you see any mistake in version 1?
> > https://lore.kernel.org/patchwork/patch/1128510/
>
> Hi Navid,
> Both the revisions of the patch are invalid. skb is freed in both the cases of
> failure and success through c4iw_ofld_send().
> case success: in ctrl_xmit()
> case failure: in c4iw_ofld_send()
>
> Thanks,
> Bharat.
>
>
> >
> >
> > Thanks,
> > Navid
> >
> > On Tue, Oct 1, 2019 at 8:54 AM Jason Gunthorpe <jgg@...pe.ca> wrote:
> > >
> > > On Mon, Sep 23, 2019 at 10:52:59AM -0500, Navid Emamdoost wrote:
> > > > In create_cq, the allocated skb buffer needs to be released on error
> > > > path.
> > > > Moved the kfree_skb(skb) under err4 label.
> > >
> > > This didn't move anything
> > >
> > > > Signed-off-by: Navid Emamdoost <navid.emamdoost@...il.com>
> > > >  drivers/infiniband/hw/cxgb4/cq.c | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/drivers/infiniband/hw/cxgb4/cq.c b/drivers/infiniband/hw/cxgb4/cq.c
> > > > index b1bb61c65f4f..1886c1af10bc 100644
> > > > +++ b/drivers/infiniband/hw/cxgb4/cq.c
> > > > @@ -173,6 +173,7 @@ static int create_cq(struct c4iw_rdev *rdev, struct t4_cq *cq,
> > > >  err4:
> > > >       dma_free_coherent(&rdev->lldi.pdev->dev, cq->memsize, cq->queue,
> > > >                         dma_unmap_addr(cq, mapping));
> > > > +     kfree_skb(skb);
> > > >  err3:
> > > >       kfree(cq->sw_queue);
> > > >  err2:
> > >
> > > This looks wrong to me:
> > >
> > > int c4iw_ofld_send(struct c4iw_rdev *rdev, struct sk_buff *skb)
> > > {
> > >         int     error = 0;
> > >
> > >         if (c4iw_fatal_error(rdev)) {
> > >                 kfree_skb(skb);
> > >                 pr_err("%s - device in error state - dropping\n", __func__);
> > >                 return -EIO;
> > >         }
> > >         error = cxgb4_ofld_send(rdev->lldi.ports[0], skb);
> > >         if (error < 0)
> > >                 kfree_skb(skb);
> > >         return error < 0 ? error : 0;
> > > }
> > >
> > > Jason
> >
> >
> >
> > --
> > Navid.



-- 
Navid.