Re: [PATCH net] net: phy: Fix possible NULL pointer dereference issues caused by phy_attached_info_irq

[Kunwu Chan]

Thanks for your reply.

On 2024/1/12 23:32, Andrew Lunn wrote:
> On Fri, Jan 12, 2024 at 05:57:24PM +0800, Kunwu Chan wrote:
> > kasprintf() returns a pointer to dynamically allocated memory
> > which can be NULL upon failure. Ensure the allocation was successful
> > by checking the pointer validity.
> >
> > Fixes: e27f178793de ("net: phy: Added IRQ print to phylink_bringup_phy()")
> > Signed-off-by: Kunwu Chan <chentao@xxxxxxxxxx>
> > ---
> >   drivers/net/phy/phy_device.c | 3 +++
> >   drivers/net/phy/phylink.c    | 2 ++
> >   2 files changed, 5 insertions(+)
> >
> > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> > index 3611ea64875e..10fa99d957c0 100644
> > --- a/drivers/net/phy/phy_device.c
> > +++ b/drivers/net/phy/phy_device.c
> > @@ -1299,6 +1299,9 @@ void phy_attached_print(struct phy_device *phydev, const char *fmt, ...)
> >   	const char *unbound = phydev->drv ? "" : "[unbound] ";
> >   	char *irq_str = phy_attached_info_irq(phydev);
> >   
> > +	if (!irq_str)
> > +		return;
> > +
> >   	if (!fmt) {
> >   		phydev_info(phydev, ATTACHED_FMT "\n", unbound,
> >   			    phydev_name(phydev), irq_str);
>
> This part looks O.K.
>
> > diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> > index ed0b4ccaa6a6..db0a545c9468 100644
> > --- a/drivers/net/phy/phylink.c
> > +++ b/drivers/net/phy/phylink.c
> > @@ -1884,6 +1884,8 @@ static int phylink_bringup_phy(struct phylink *pl, struct phy_device *phy,
> >   	phy->phy_link_change = phylink_phy_change;
> >   
> >   	irq_str = phy_attached_info_irq(phy);
> > +	if (!irq_str)
> > +		return -ENOMEM;
>
> Here, i would just skip the print and continue with the reset of the
> function. The print is just useful information, its not a big problem
> if its not printed. However, if this function does not complete, the
> network interface is likely to be dead.
Thanks for the reminder.
The second part doesn't look so perfect, can we just print an empty 
string when the irq_str is empty?

--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1886,7 +1886,7 @@ static int phylink_bringup_phy(struct phylink *pl, 
struct phy_device *phy,
        irq_str = phy_attached_info_irq(phy);
        phylink_info(pl,
                     "PHY [%s] driver [%s] (irq=%s)\n",
-                    dev_name(&phy->mdio.dev), phy->drv->name, irq_str);
+                    dev_name(&phy->mdio.dev), phy->drv->name, irq_str ? 
irq_str : "");
        kfree(irq_str);

> 	Andrew
--
Thanks,
  Kunwu