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SubjectRe: [PATCH v2 2/8] phy: mvebu-cp110-comphy: fix port check in ->xlate()
Hi Russell,

Russell King - ARM Linux <linux@armlinux.org.uk> wrote on Mon, 3 Dec
2018 00:36:23 +0000:

> On Sun, Dec 02, 2018 at 08:35:09PM +0100, Miquel Raynal wrote:
> > Hi Russell,
> >
> > Russell King - ARM Linux <linux@armlinux.org.uk> wrote on Fri, 30 Nov
> > 2018 19:00:31 +0000:
> >
> > > On Fri, Nov 30, 2018 at 03:47:37PM +0100, Miquel Raynal wrote:
> > > > So far the PHY ->xlate() callback was checking if the port was
> > > > "invalid" before continuing, meaning that the port has not been used
> > > > yet. This check is not correct as there is no opposite call to
> > > > ->xlate() once the PHY is released by the user and the port will
> > > > remain "valid" after the first phy_get()/phy_put() calls. Hence, if
> > > > this driver is built as a module, inserted, removed and inserted
> > > > again, the PHY will appear busy and the second probe will fail.
> > > >
> > > > To fix this, just drop the faulty check and instead verify that the
> > > > port number is valid (ie. in the possible range).
> > > >
> > > > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > > > ---
> > > > drivers/phy/marvell/phy-mvebu-cp110-comphy.c | 4 ++--
> > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/phy/marvell/phy-mvebu-cp110-comphy.c b/drivers/phy/marvell/phy-mvebu-cp110-comphy.c
> > > > index 31b9a1c18345..a40b876ff214 100644
> > > > --- a/drivers/phy/marvell/phy-mvebu-cp110-comphy.c
> > > > +++ b/drivers/phy/marvell/phy-mvebu-cp110-comphy.c
> > > > @@ -567,9 +567,9 @@ static struct phy *mvebu_comphy_xlate(struct device *dev,
> > > > return phy;
> > > >
> > > > lane = phy_get_drvdata(phy);
> > > > - if (lane->port >= 0)
> > > > - return ERR_PTR(-EBUSY);
> > > > lane->port = args->args[0];
> > > > + if (lane->port >= MVEBU_COMPHY_PORTS)
> > > > + return ERR_PTR(-EINVAL);
> > >
> > > Shouldn't we validate args->args[0] before doing anything?
> > >
> >
> > I don't understand your point, there is a check on args->args[0] as
> > we check its value (through lane->port) right after. What do you
> > have in mind?
>
> Right, there is already a check on args->args[0] for it being greater
> than MVEBU_COMPHY_PORTS and returning an error (and in fact warning
> if that is the case). So in that case, what is the use of the above
> additional test you are proposing to add? The resulting code ends up
> looking like this:
>
> if (WARN_ON(args->args[0] >= MVEBU_COMPHY_PORTS))
> return ERR_PTR(-EINVAL);
> ...
> lane->port = args->args[0];
> + if (lane->port >= MVEBU_COMPHY_PORTS)
> + return ERR_PTR(-EINVAL);
>
> which is just silly - the second test can never be evaluated as true,
> and therefore is redundant.
>
> In any case, my point was that in your patch, where you assign
> lane->port and then validate the lane->port value, this is in
> principle the wrong order - the order should always be: validate
> first, then make use.
>

You are right, this test is redundant; I forgot about the first
check. I will just drop these additional two lines and just do:

[...]
lane->port = args->args[0];

return 0;
}

Thanks,
Miquèl
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