[lvc-project] [PATCH] i2c: Fix NULL pointer dereference in npcm_i2c_reg_slave

[Fedor Pchelkin]

On 24/01/10 10:43AM, Tali Perry wrote:
> On Tue, Jan 9, 2024 at 4:52 PM Rand Deeb <rand.sec96 at gmail.com> wrote:
> >
> > In the npcm_i2c_reg_slave function, a potential NULL pointer dereference
> > issue occurs when 'client' is NULL. This patch adds a proper NULL check for
> > 'client' at the beginning of the function to prevent undefined behavior.
> >
> > Found by Linux Verification Center (linuxtesting.org) with SVACE.
> >
> > Signed-off-by: Rand Deeb <rand.sec96 at gmail.com>
> > ---
> >  drivers/i2c/busses/i2c-npcm7xx.c | 9 +++++----
> >  1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> > index c1b679737240..cfabfb50211d 100644
> > --- a/drivers/i2c/busses/i2c-npcm7xx.c
> > +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> > @@ -1243,13 +1243,14 @@ static irqreturn_t npcm_i2c_int_slave_handler(struct npcm_i2c *bus)
> >  static int npcm_i2c_reg_slave(struct i2c_client *client)
> >  {
> >         unsigned long lock_flags;
> > -       struct npcm_i2c *bus = i2c_get_adapdata(client->adapter);
> > -
> > -       bus->slave = client;
> > +       struct npcm_i2c *bus;
> >
> > -       if (!bus->slave)
> > +       if (!client)
> >                 return -EINVAL;
> >
> > +       bus = i2c_get_adapdata(client->adapter);
> > +       bus->slave = client;
> > +
> >         if (client->flags & I2C_CLIENT_TEN)
> >                 return -EAFNOSUPPORT;
> >
> > --
> > 2.34.1
> >
> 
> 
> Thanks for the patch!
> 
> Reviewed-by:tali.perry1 at gmail.com

If I'm not missing something, npcm_i2c_reg_slave() is called via a
function pointer ->reg_slave here [1]. And seems `client` can't be NULL
there. Other drivers implementing ->reg_slave function don't check its
argument.

Maybe we should just drop `if (!bus->slave)` check?

[1]: https://elixir.bootlin.com/linux/latest/source/drivers/i2c/i2c-core-slave.c#L48