Message-ID: <78b980a9e913cb6d98fd7f99218ccb815926c9f3.camel@gmail.com>
Subject: Re: [PATCH] driver: core: Prevent NULL pointer dereference in
 device name functions
From:   Alexander Sverdlin <alexander.sverdlin@gmail.com>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org,
        "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Mon, 13 Feb 2023 08:12:08 +0100
In-Reply-To: <Y+nhnauiUDspXwNM@kroah.com>
References: <20230212220441.258258-1-alexander.sverdlin@gmail.com>
         <Y+nhnauiUDspXwNM@kroah.com>
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Hi Greg,

On Mon, 2023-02-13 at 08:07 +0100, Greg Kroah-Hartman wrote:
> > Prevent similar scenarios:
> >=20
> > Unable to handle kernel NULL pointer dereference at virtual address 000=
00038
> > ...
> > PC is at dev_driver_string+0x0/0x38
>=20
> How did this "scenario" happen?=C2=A0 What in-tree code caused this?
>=20

such in-tree code is not known to me, I stubled upon this putting dev_info(=
)
all over the code in the platform we currently convert to DT (cirrus ep93xx=
).

> > Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
> > ---
> > =C2=A0 drivers/base/core.c=C2=A0=C2=A0=C2=A0 | 3 +++
> > =C2=A0 include/linux/device.h | 5 +++++
> > =C2=A0 2 files changed, 8 insertions(+)
> >=20
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index a3e14143ec0c..4ff2ddea7c9b 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -2174,6 +2174,9 @@ const char *dev_driver_string(const struct device=
 *dev)
> > =C2=A0 {
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct device_driver *d=
rv;
> > =C2=A0=20
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (!dev)
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0return "<null>";
> > +
>=20
> None of these functions should be called with a NULL pointer as the
> reference should have been properly gotten on them before calling these
> functions.=C2=A0 So let's fix up the callers please, something is really
> wrong with them.=C2=A0 Again, what in-tree code is causing this to happen=
?

Thanks for the explanation!

--=20
Alexander Sverdlin.