linux-kernel - Re: [PATCH] staging: board: drop refcount in success case

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Message-ID: <20180619080834.GA31882@osadl.at>
Date:   Tue, 19 Jun 2018 08:08:34 +0000
From:   Nicholas Mc Guire <der.herr@...r.at>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Nicholas Mc Guire <hofrat@...dl.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        driverdevel <devel@...verdev.osuosl.org>,
        natechancellor@...il.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH] staging: board: drop refcount in success case

On Tue, Jun 19, 2018 at 09:51:44AM +0200, Geert Uytterhoeven wrote:
> On Tue, Jun 19, 2018 at 9:37 AM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> > On Mon, Jun 18, 2018 at 08:53:19PM +0200, Nicholas Mc Guire wrote:
> > >  The call to of_find_compatible_node() returns irqc_node with refcount
> > > incremented thus it must be explicitly decremented here after it was
> > > checked for non-NULL.
> > >
> > > Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
> > > Fixes: commit 72ee8626eeb1 ("staging: board: Add support for translating hwirq to virq numbers")
> > > ---
> > >
> > > Problem located with an experimental coccinelle script
> > >
> > > Patch was compile-tested with: x86_64_defconfig + STAGING=y, STAGING_BOARD=y
> > >
> > > Patch is against 4.18-rc1 (localversion-next is next-20180618)
> > >
> > >  drivers/staging/board/board.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/staging/board/board.c b/drivers/staging/board/board.c
> > > index cb6feb3..8ee48e5 100644
> > > --- a/drivers/staging/board/board.c
> > > +++ b/drivers/staging/board/board.c
> > > @@ -64,12 +64,13 @@ int __init board_staging_gic_setup_xlate(const char *gic_match,
> > >       irqc_node = of_find_compatible_node(NULL, NULL, gic_match);
> > >
> > >       WARN_ON(!irqc_node);
> > >       if (!irqc_node)
> > >               return -ENOENT;
> > >
> > > +     of_node_put(irqc_node);
> >
> > I don't feel like this is the right thing...  We should keep the
> > reference until we're done with it.  Which apparently is never?
> 
> Indeed. The reference must not be released in this function, as it's stored in
> a global variable, and used later.

yup -  I had simply interpreted this incorrectly as checking only and
overlooked that this was a global variable.

> 
> As all users are __init, it could be released when the init section is freeed,
> in theory, but there's no callback for that.
> 
> Hence:
> NAKed-by: Geert Uytterhoeven <geert+renesas@...der.be>
>
thanks for the clarification - sorry for the noise.

thx
hofrat