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To:     Brian Norris <briannorris@chromium.org>
From:   Stephen Boyd <swboyd@chromium.org>
In-Reply-To: <20180809174936.GC129285@ban.mtv.corp.google.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org,
        Wei-Ning Huang <wnhuang@chromium.org>,
        Julius Werner <jwerner@chromium.org>,
        Samuel Holland <samuel@sholland.org>
References: <20180809171722.144325-1-swboyd@chromium.org>
 <20180809171722.144325-3-swboyd@chromium.org>
 <20180809174936.GC129285@ban.mtv.corp.google.com>
Message-ID: <153384363124.220756.3747855789935101539@swboyd.mtv.corp.google.com>
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Subject: Re: [PATCH v3 2/7] firmware: coreboot: Unmap ioregion on failure
Date:   Thu, 09 Aug 2018 12:40:31 -0700
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Quoting Brian Norris (2018-08-09 10:49:38)
> On Thu, Aug 09, 2018 at 10:17:17AM -0700, Stephen Boyd wrote:
> > Both callers of coreboot_table_init() ioremap the pointer that comes in
> > but they don't unmap the memory on failure. Both of them also fail probe
> > immediately with the return value of coreboot_table_init(), leaking a
> > mapping when it fails. Plug the leak so the mapping isn't left unused.
> > =

> > Cc: Wei-Ning Huang <wnhuang@chromium.org>
> > Cc: Julius Werner <jwerner@chromium.org>
> > Cc: Brian Norris <briannorris@chromium.org>
> > Cc: Samuel Holland <samuel@sholland.org>
> > Fixes: 570d30c2823f ("firmware: coreboot: Expose the coreboot table as =
a bus")
> =

> I suppose this is fair, since that commit introduced error paths and
> didn't clean them up. But one warning below:
> =

> > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> > ---
> >  drivers/firmware/google/coreboot_table.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > =

> > diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmwar=
e/google/coreboot_table.c
> > index 19db5709ae28..0d3e140444ae 100644
> > --- a/drivers/firmware/google/coreboot_table.c
> > +++ b/drivers/firmware/google/coreboot_table.c
> > @@ -138,6 +138,9 @@ int coreboot_table_init(struct device *dev, void __=
iomem *ptr)
> >               ptr_entry +=3D entry.size;
> >       }
> >  =

> > +     if (ret)
> > +             iounmap(ptr);
> =

> This works because no sub-driver is using this mapping any more (i.e.,
> because we killed coreboot_table_find()). Otherwise, we'd need to
> explicitly kill all the sub-devices first. IOW, if this gets backported
> to older kernels, it would need to go along with this and its other
> dependencies:

The memory is copied out of the table. So do the devices actually use
the memory that we remap here? I don't see how it's a problem if we
unmap the table after we populate devices.

> =

> b616cf53aa7a firmware: coreboot: Remove unused coreboot_table_find
> =

> But I guess that's a question for -stable. Or, we remove the 'Fixes'
> tag? Or add another tag, to list other dependencies? Or just ignore it.
> =

> But for this change as applied to mainline:
> =

> Reviewed-by: Brian Norris <briannorris@chromium.org>
> =


Thanks!