linux-kernel - Re: [PATCH net] net: phy: Fix possible NULL pointer dereference issues caused by phy_attached_info

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Message-ID: <627c9558-04df-43a6-b6e4-a13f24a8bc1d@lunn.ch>
Date: Fri, 12 Jan 2024 16:32:14 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Kunwu Chan <chentao@...inos.cn>
Cc: hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	f.fainelli@...il.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: phy: Fix possible NULL pointer dereference
 issues caused by phy_attached_info_irq

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@...inos.cn>
> ---
>  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.

	Andrew