linux-kernel - Re: [PATCH] net: mdio-ipq4019: fix possible invalid pointer dereference

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Message-ID: <d31663c5-8ac1-f424-b0ad-737e86b4595b@huawei.com>
Date:   Thu, 17 Nov 2022 16:50:46 +0800
From:   Hui Tang <tanghui20@...wei.com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <mw@...ihalf.com>, <linux@...linux.org.uk>, <pabeni@...hat.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <yusongping@...wei.com>
Subject: Re: [PATCH] net: mdio-ipq4019: fix possible invalid pointer
 dereference



On 2022/11/15 21:36, Andrew Lunn wrote:
> On Tue, Nov 15, 2022 at 12:50:28PM +0800, Hui Tang wrote:
>> priv->eth_ldo_rdy is saved the return value of devm_ioremap_resource(),
>> which !IS_ERR() should be used to check.
>>
>> Fixes: 23a890d493e3 ("net: mdio: Add the reset function for IPQ MDIO driver")
>> Signed-off-by: Hui Tang <tanghui20@...wei.com>
>> ---
>>  drivers/net/mdio/mdio-ipq4019.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/mdio/mdio-ipq4019.c b/drivers/net/mdio/mdio-ipq4019.c
>> index 4eba5a91075c..d7a1f7c56f97 100644
>> --- a/drivers/net/mdio/mdio-ipq4019.c
>> +++ b/drivers/net/mdio/mdio-ipq4019.c
>> @@ -188,7 +188,7 @@ static int ipq_mdio_reset(struct mii_bus *bus)
>>  	/* To indicate CMN_PLL that ethernet_ldo has been ready if platform resource 1
>>  	 * is specified in the device tree.
>>  	 */
>> -	if (priv->eth_ldo_rdy) {
>> +	if (!IS_ERR(priv->eth_ldo_rdy)) {
>>  		val = readl(priv->eth_ldo_rdy);
>>  		val |= BIT(0);
>>  		writel(val, priv->eth_ldo_rdy);
>
> There is a general pattern in the kernel that optional things are set
> to NULL if the resource does not exist. Often there is a
> get_foo_optional() which will return a NULL point if the things does
> not exist, the thing if it does exist, or an error code if a real
> error happened.
>
> So please follow this patterns. Check the return value in
> ipq4019_mdio_probe(). Looking at __devm_ioremap_resource() i _think_
> it returns -ENOMEM if the resource does not exist? So maybe any other
> error is a real error, and should be reported, and -ENOMEM should
> result in eth_ldo_rdy set to NULL?

Thanks, I will resend it according to the style you said.