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References: <20190923050823.GL14368@unreal> <20190923155300.20407-1-navid.emamdoost@gmail.com>
 <20191001135430.GA27086@ziepe.ca>
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From:   Navid Emamdoost <navid.emamdoost@gmail.com>
Date:   Wed, 2 Oct 2019 16:35:06 -0500
Message-ID: <CAEkB2EQF0D-Fdg74+E4VdxipZvTaBKseCtKJKnFg7T6ZZE9x6Q@mail.gmail.com>
Subject: Re: [PATCH v2] RDMA: release allocated skb
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     Leon Romanovsky <leon@kernel.org>,
        Navid Emamdoost <emamd001@umn.edu>,
        Stephen McCamant <smccaman@umn.edu>, Kangjie Lu <kjlu@umn.edu>,
        Potnuri Bharat Teja <bharat@chelsio.com>,
        Doug Ledford <dledford@redhat.com>, linux-rdma@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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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/


Thanks,
Navid

On Tue, Oct 1, 2019 at 8:54 AM Jason Gunthorpe <jgg@ziepe.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@gmail.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.