[PATCH v2] drm/bridge: megachips: Fix error handling in i2c_register_driver()

[Robert Foss]

On Wed, 23 Nov 2022 at 07:40, Ian Ray <ian.ray at ge.com> wrote:
>
> On Tue, Nov 08, 2022 at 09:12:26AM +0000, Yuan Can wrote:
> >
> > A problem about insmod megachips-stdpxxxx-ge-b850v3-fw.ko failed is
> > triggered with the following log given:
> >
> > [ 4497.981497] Error: Driver 'stdp4028-ge-b850v3-fw' is already registered, aborting...
> > insmod: ERROR: could not insert module megachips-stdpxxxx-ge-b850v3-fw.ko: Device or resource busy
> >
> > The reason is that stdpxxxx_ge_b850v3_init() returns i2c_add_driver()
> > directly without checking its return value, if i2c_add_driver() failed,
> > it returns without calling i2c_del_driver() on the previous i2c driver,
> > resulting the megachips-stdpxxxx-ge-b850v3-fw can never be installed
> > later.
> > A simple call graph is shown as below:
> >
> >  stdpxxxx_ge_b850v3_init()
> >    i2c_add_driver(&stdp4028_ge_b850v3_fw_driver)
> >    i2c_add_driver(&stdp2690_ge_b850v3_fw_driver)
> >      i2c_register_driver()
> >        driver_register()
> >          bus_add_driver()
> >            priv = kzalloc(...) # OOM happened
> >    # return without delete stdp4028_ge_b850v3_fw_driver
> >
> > Fix by calling i2c_del_driver() on stdp4028_ge_b850v3_fw_driver when
> > i2c_add_driver() returns error.
> >
>
> Thank you!
>
> > Fixes: fcfa0ddc18ed ("drm/bridge: Drivers for megachips-stdpxxxx-ge-b850v3-fw (LVDS-DP++)")
> > Signed-off-by: Yuan Can <yuancan at huawei.com>
> > Reviewed-by: Andrzej Hajda <andrzej.hajda at intel.com>
>
> Tested-by: Ian Ray <ian.ray at ge.com>
>
> > ---
> > Changes in v2:
> > - Add Andrzej's Reviewed-by
> > - Change to the new error return style suggested by Andrzej
> >
> >  drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
> > index 97359f807bfc..cbfa05a6767b 100644
> > --- a/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
> > +++ b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
> > @@ -440,7 +440,11 @@ static int __init stdpxxxx_ge_b850v3_init(void)
> >       if (ret)
> >               return ret;
> >
> > -     return i2c_add_driver(&stdp2690_ge_b850v3_fw_driver);
> > +     ret = i2c_add_driver(&stdp2690_ge_b850v3_fw_driver);
> > +     if (ret)
> > +             i2c_del_driver(&stdp4028_ge_b850v3_fw_driver);
> > +
> > +     return ret;
> >  }
> >  module_init(stdpxxxx_ge_b850v3_init);
> >
> > --
> > 2.17.1
> >

Applied to drm-misc-next.