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

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Message-ID: <b71c5e28-2dbe-48c8-ab92-e1dad9d6f2e4@kylinos.cn>
Date: Mon, 15 Jan 2024 11:02:09 +0800
From: Kunwu Chan <chentao@...inos.cn>
To: Andrew Lunn <andrew@...n.ch>
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

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@...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.
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