USB2NET: SR9700: fix uninitialized variable use in sr_mdio_read

[PATCH] USB2NET: SR9700: fix uninitialized variable use in sr_mdio_read

Posted by Ma Ke 1 month, 2 weeks ago

It could lead to error happen because the variable res is not updated if
the call to sr_share_read_word returns an error. In this particular case
error code was returned and res stayed uninitialized.

This can be avoided by checking the return value of sr_share_read_word
and propagating the error if the read operation failed.

Fixes: c9b37458e956 ("USB2NET : SR9700 : One chip USB 1.1 USB2NET SR9700Device Driver Support")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
 drivers/net/usb/sr9700.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/sr9700.c b/drivers/net/usb/sr9700.c
index 0a662e42ed96..d5bc596f4521 100644
--- a/drivers/net/usb/sr9700.c
+++ b/drivers/net/usb/sr9700.c
@@ -179,6 +179,7 @@ static int sr_mdio_read(struct net_device *netdev, int phy_id, int loc)
 	struct usbnet *dev = netdev_priv(netdev);
 	__le16 res;
 	int rc = 0;
+	int err;
 
 	if (phy_id) {
 		netdev_dbg(netdev, "Only internal phy supported\n");
@@ -193,7 +194,10 @@ static int sr_mdio_read(struct net_device *netdev, int phy_id, int loc)
 		if (value & NSR_LINKST)
 			rc = 1;
 	}
-	sr_share_read_word(dev, 1, loc, &res);
+	err = sr_share_read_word(dev, 1, loc, &res);
+	if (err < 0)
+		return err;
+
 	if (rc == 1)
 		res = le16_to_cpu(res) | BMSR_LSTATUS;
 	else
-- 
2.25.1

Re: [PATCH] USB2NET: SR9700: fix uninitialized variable use in sr_mdio_read

Posted by Shigeru Yoshida 1 month, 2 weeks ago

On Tue, 23 Jul 2024 22:04:34 +0800, Ma Ke wrote:
> It could lead to error happen because the variable res is not updated if
> the call to sr_share_read_word returns an error. In this particular case
> error code was returned and res stayed uninitialized.
> 
> This can be avoided by checking the return value of sr_share_read_word
> and propagating the error if the read operation failed.
> 
> Fixes: c9b37458e956 ("USB2NET : SR9700 : One chip USB 1.1 USB2NET SR9700Device Driver Support")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
> ---
>  drivers/net/usb/sr9700.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/usb/sr9700.c b/drivers/net/usb/sr9700.c
> index 0a662e42ed96..d5bc596f4521 100644
> --- a/drivers/net/usb/sr9700.c
> +++ b/drivers/net/usb/sr9700.c
> @@ -179,6 +179,7 @@ static int sr_mdio_read(struct net_device *netdev, int phy_id, int loc)
>  	struct usbnet *dev = netdev_priv(netdev);
>  	__le16 res;
>  	int rc = 0;
> +	int err;
>  
>  	if (phy_id) {
>  		netdev_dbg(netdev, "Only internal phy supported\n");
> @@ -193,7 +194,10 @@ static int sr_mdio_read(struct net_device *netdev, int phy_id, int loc)
>  		if (value & NSR_LINKST)
>  			rc = 1;
>  	}
> -	sr_share_read_word(dev, 1, loc, &res);
> +	err = sr_share_read_word(dev, 1, loc, &res);
> +	if (err < 0)
> +		return err;
> +

The patch looks good to me.  But I think the following sr_read_reg()
has the same uninit-value access issue.  If sr_read_reg() returns an
error, value may be uninitialized:

static int sr_mdio_read(struct net_device *netdev, int phy_id, int loc)
{
[...]
	/* Access NSR_LINKST bit for link status instead of MII_BMSR */
	if (loc == MII_BMSR) {
		u8 value;

		sr_read_reg(dev, SR_NSR, &value);
		if (value & NSR_LINKST)
			rc = 1;
	}

Why don't we fix it together?

Thanks,
Shigeru

>  	if (rc == 1)
>  		res = le16_to_cpu(res) | BMSR_LSTATUS;
>  	else
> -- 
> 2.25.1
> 
>

Re: [PATCH] USB2NET: SR9700: fix uninitialized variable use in sr_mdio_read

Posted by Simon Horman 1 month, 2 weeks ago

On Tue, Jul 23, 2024 at 10:04:34PM +0800, Ma Ke wrote:
> It could lead to error happen because the variable res is not updated if
> the call to sr_share_read_word returns an error. In this particular case
> error code was returned and res stayed uninitialized.
> 
> This can be avoided by checking the return value of sr_share_read_word
> and propagating the error if the read operation failed.
> 
> Fixes: c9b37458e956 ("USB2NET : SR9700 : One chip USB 1.1 USB2NET SR9700Device Driver Support")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>

Hi Ma Ke,

As this is a fix, with a fixes tag (good!), it should probably be targeted
at the net tree (as opposed to net-next). The target tree for
networking patches should be included in the Subject.

	Subject: [PATCH net] ...

Looking at git history, it seems that an appropriate prefix for this patch
would be net: "net: usb: sr9700: "

	Subject: [PATCH net] net: usb: sr9700: ...

And, skipping ahead, please do consider reading, especially the bit about 24h.
https://docs.kernel.org/process/maintainer-netdev.html

> ---
>  drivers/net/usb/sr9700.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/usb/sr9700.c b/drivers/net/usb/sr9700.c
> index 0a662e42ed96..d5bc596f4521 100644
> --- a/drivers/net/usb/sr9700.c
> +++ b/drivers/net/usb/sr9700.c
> @@ -179,6 +179,7 @@ static int sr_mdio_read(struct net_device *netdev, int phy_id, int loc)
>  	struct usbnet *dev = netdev_priv(netdev);
>  	__le16 res;
>  	int rc = 0;
> +	int err;
>  
>  	if (phy_id) {
>  		netdev_dbg(netdev, "Only internal phy supported\n");
> @@ -193,7 +194,10 @@ static int sr_mdio_read(struct net_device *netdev, int phy_id, int loc)
>  		if (value & NSR_LINKST)
>  			rc = 1;
>  	}
> -	sr_share_read_word(dev, 1, loc, &res);
> +	err = sr_share_read_word(dev, 1, loc, &res);
> +	if (err < 0)
> +		return err;
> +

I agree that this fixes a possible error condition.
But I wonder if there are not more similar problems in this
file. E.g. the call to sr_read_reg() which seeds value
which is used at the top of this hunk.

>  	if (rc == 1)
>  		res = le16_to_cpu(res) | BMSR_LSTATUS;
>  	else
> -- 
> 2.25.1
> 
>

Re: [PATCH] USB2NET: SR9700: fix uninitialized variable use in sr_mdio_read

Posted by Greg KH 1 month, 2 weeks ago

On Tue, Jul 23, 2024 at 10:04:34PM +0800, Ma Ke wrote:
> It could lead to error happen because the variable res is not updated if
> the call to sr_share_read_word returns an error. In this particular case
> error code was returned and res stayed uninitialized.
> 
> This can be avoided by checking the return value of sr_share_read_word
> and propagating the error if the read operation failed.
> 
> Fixes: c9b37458e956 ("USB2NET : SR9700 : One chip USB 1.1 USB2NET SR9700Device Driver Support")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>

You forgot to document how you found this problem.

> ---
>  drivers/net/usb/sr9700.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
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You are receiving this message because of the following common error(s)
as indicated below:

- You have marked a patch with a "Fixes:" tag for a commit that is in an
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  signed-off-by area at all, which means that the patch will not be
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  Documentation/process/stable-kernel-rules.rst file for how to resolve
  this.

If you wish to discuss this problem further, or you have questions about
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thanks,

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