linux-kernel - Re: [PATCH -next] IB/qib: Add missing err handle for qib_user_sdma_rb

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Message-ID: <20190102192211.GJ5424@mtr-leonro.mtl.com>
Date:   Wed, 2 Jan 2019 21:22:11 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     YueHaibing <yuehaibing@...wei.com>, dennis.dalessandro@...el.com,
        mike.marciniszyn@...el.com, dledford@...hat.com,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH -next] IB/qib: Add missing err handle for
 qib_user_sdma_rb_insert

On Wed, Jan 02, 2019 at 12:07:40PM -0700, Jason Gunthorpe wrote:
> On Wed, Jan 02, 2019 at 08:40:50PM +0200, Leon Romanovsky wrote:
> > On Wed, Jan 02, 2019 at 10:12:24AM -0700, Jason Gunthorpe wrote:
> > > On Fri, Dec 21, 2018 at 10:19:38AM +0800, YueHaibing wrote:
> > > > It should goto err handle if qib_user_sdma_rb_insert fails,
> > > > other than success return.
> > > >
> > > > Fixes: 67810e8c3c01 ("RDMA/qib: Remove all occurrences of BUG_ON()")
> > > > Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> > > >  drivers/infiniband/hw/qib/qib_user_sdma.c | 2 ++
> > > >  1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/drivers/infiniband/hw/qib/qib_user_sdma.c b/drivers/infiniband/hw/qib/qib_user_sdma.c
> > > > index 31c523b..e87c0a7 100644
> > > > +++ b/drivers/infiniband/hw/qib/qib_user_sdma.c
> > > > @@ -237,6 +237,8 @@ qib_user_sdma_queue_create(struct device *dev, int unit, int ctxt, int sctxt)
> > > >
> > > >  		ret = qib_user_sdma_rb_insert(&qib_user_sdma_rb_root,
> > > >  					sdma_rb_node);
> > > > +		if (ret == 0)
> > > > +			goto err_rb;
> > > >  	}
> > >
> > > This doesn't look right, what about undoing the kmalloc directly
> > > above?
> >
> > Back then, I came to conclusion that qib_user_sdma_rb_insert() never
> > returns 0. Otherwise, Dennis would see that BUG_ON() for a long time
> > ago.
>
> It fails if the index is in the RB tree, which would indicate a
> programming bug.

I tried to say that this programming bug doesn't exist in the reality.

>
> The way to replace the BUG_ON is something like:
>
> if (WARN_ON(ret == 0)) {
>     kfree()
>     goto err_rb;
> }
>
> Jason

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