diff mbox series

[Linux-kernel-mentees] net: usb: rtl8150: prevent set_ethernet_addr from setting uninit address

Message ID 20200929082028.50540-1-anant.thazhemadam@gmail.com (mailing list archive)
State Superseded
Headers show
Series [Linux-kernel-mentees] net: usb: rtl8150: prevent set_ethernet_addr from setting uninit address | expand

Commit Message

Anant Thazhemadam Sept. 29, 2020, 8:20 a.m. UTC 
When get_registers() fails (which happens when usb_control_msg() fails)
in set_ethernet_addr(), the uninitialized value of node_id gets copied
as the address.

Checking for the return values appropriately, and handling the case
wherein set_ethernet_addr() fails like this, helps in avoiding the
mac address being incorrectly set in this manner.

Reported-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
Tested-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
---
 drivers/net/usb/rtl8150.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

Comments

Anant Thazhemadam Sept. 29, 2020, 8:46 a.m. UTC | #1 
A sample crash report can be found here.
    https://syzkaller.appspot.com/text?tag=CrashReport&x=17486911900000

The line where the bug seems to get triggered is,

if (!batadv_compare_eth(hard_iface->net_dev->dev_addr,
                    net_dev->dev_addr))
Looks like it goes through the list of ethernet interfaces, and
compares it with the address of the new device; which can
end up going uninitialized too.

The address should have been set by set_ethernet_addr:

    static inline void set_ethernet_addr(rtl8150_t * dev)
    {
        u8 node_id[6];

        get_registers(dev, IDR, sizeof(node_id), node_id);
        memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
    }

However, when get_registers() fails (when ret <= 0 or ret > size),
no memory is copied back into node_id, which remains uninitialized.
The address is then set to be this uninitialized node_id value.

Checking for the return value of get_registers() in set_ethernet_addr()
and further checking the value of set_ethernet_addr() where ever it has
been invoked, and handling the condition wherein get_registers() fails
appropriately helps solve this issue.
Thank you for your time.

Thanks,
Anant
Petko Manolov Sept. 29, 2020, 8:47 a.m. UTC | #2 
On 20-09-29 13:50:28, Anant Thazhemadam wrote:
> When get_registers() fails (which happens when usb_control_msg() fails)
> in set_ethernet_addr(), the uninitialized value of node_id gets copied
> as the address.
> 
> Checking for the return values appropriately, and handling the case
> wherein set_ethernet_addr() fails like this, helps in avoiding the
> mac address being incorrectly set in this manner.
> 
> Reported-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
> Tested-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
> ---
>  drivers/net/usb/rtl8150.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
> index 733f120c852b..e542a9ab2ff8 100644
> --- a/drivers/net/usb/rtl8150.c
> +++ b/drivers/net/usb/rtl8150.c
> @@ -150,7 +150,7 @@ static const char driver_name [] = "rtl8150";
>  **	device related part of the code
>  **
>  */
> -static int get_registers(rtl8150_t * dev, u16 indx, u16 size, void *data)
> +static int get_registers(rtl8150_t *dev, u16 indx, u16 size, void *data)
>  {
>  	void *buf;
>  	int ret;
> @@ -274,12 +274,17 @@ static int write_mii_word(rtl8150_t * dev, u8 phy, __u8 indx, u16 reg)
>  		return 1;
>  }
>  
> -static inline void set_ethernet_addr(rtl8150_t * dev)
> +static bool set_ethernet_addr(rtl8150_t *dev)
>  {
>  	u8 node_id[6];
> +	int ret;
>  
> -	get_registers(dev, IDR, sizeof(node_id), node_id);
> -	memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
> +	ret = get_registers(dev, IDR, sizeof(node_id), node_id);
> +	if (ret > 0 && ret <= sizeof(node_id)) {

get_registers() was recently modified to use usb_control_msg_recv() which does
not return partial reads.  IOW you'll either get negative value or
sizeof(node_id).  Since it is good to be paranoid i'd convert the above check
to:

	if (ret == sizeof(node_id)) {

and fail in any other case.  Apart from this minor detail the rest of the patch 
looks good to me.

Acked-by: Petko Manolov
Anant Thazhemadam Sept. 30, 2020, 4:02 a.m. UTC | #3 
On 29/09/20 2:17 pm, Petko Manolov wrote:
> On 20-09-29 13:50:28, Anant Thazhemadam wrote:
>> When get_registers() fails (which happens when usb_control_msg() fails)
>> in set_ethernet_addr(), the uninitialized value of node_id gets copied
>> as the address.
>>
>> Checking for the return values appropriately, and handling the case
>> wherein set_ethernet_addr() fails like this, helps in avoiding the
>> mac address being incorrectly set in this manner.
>>
>> Reported-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
>> Tested-by: syzbot+abbc768b560c84d92fd3@syzkaller.appspotmail.com
>> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
>> ---
>>  drivers/net/usb/rtl8150.c | 24 ++++++++++++++++--------
>>  1 file changed, 16 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
>> index 733f120c852b..e542a9ab2ff8 100644
>> --- a/drivers/net/usb/rtl8150.c
>> +++ b/drivers/net/usb/rtl8150.c
>> @@ -150,7 +150,7 @@ static const char driver_name [] = "rtl8150";
>>  **	device related part of the code
>>  **
>>  */
>> -static int get_registers(rtl8150_t * dev, u16 indx, u16 size, void *data)
>> +static int get_registers(rtl8150_t *dev, u16 indx, u16 size, void *data)
>>  {
>>  	void *buf;
>>  	int ret;
>> @@ -274,12 +274,17 @@ static int write_mii_word(rtl8150_t * dev, u8 phy, __u8 indx, u16 reg)
>>  		return 1;
>>  }
>>  
>> -static inline void set_ethernet_addr(rtl8150_t * dev)
>> +static bool set_ethernet_addr(rtl8150_t *dev)
>>  {
>>  	u8 node_id[6];
>> +	int ret;
>>  
>> -	get_registers(dev, IDR, sizeof(node_id), node_id);
>> -	memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
>> +	ret = get_registers(dev, IDR, sizeof(node_id), node_id);
>> +	if (ret > 0 && ret <= sizeof(node_id)) {
> get_registers() was recently modified to use usb_control_msg_recv() which does
> not return partial reads.  IOW you'll either get negative value or
> sizeof(node_id).  Since it is good to be paranoid i'd convert the above check
> to:
>
> 	if (ret == sizeof(node_id)) {
>
> and fail in any other case.  Apart from this minor detail the rest of the patch 
> looks good to me.
>
> Acked-by: Petko Manolov
Got it. I'll be sure to include this in a v2, and send that in soon enough.
Thanks for pointing that out. :)

Thanks,
Anant
diff mbox series

Patch

diff --git a/drivers/net/usb/rtl8150.c b/drivers/net/usb/rtl8150.c
index 733f120c852b..e542a9ab2ff8 100644
--- a/drivers/net/usb/rtl8150.c
+++ b/drivers/net/usb/rtl8150.c
@@ -150,7 +150,7 @@  static const char driver_name [] = "rtl8150";
 **	device related part of the code
 **
 */
-static int get_registers(rtl8150_t * dev, u16 indx, u16 size, void *data)
+static int get_registers(rtl8150_t *dev, u16 indx, u16 size, void *data)
 {
 	void *buf;
 	int ret;
@@ -274,12 +274,17 @@  static int write_mii_word(rtl8150_t * dev, u8 phy, __u8 indx, u16 reg)
 		return 1;
 }
 
-static inline void set_ethernet_addr(rtl8150_t * dev)
+static bool set_ethernet_addr(rtl8150_t *dev)
 {
 	u8 node_id[6];
+	int ret;
 
-	get_registers(dev, IDR, sizeof(node_id), node_id);
-	memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
+	ret = get_registers(dev, IDR, sizeof(node_id), node_id);
+	if (ret > 0 && ret <= sizeof(node_id)) {
+		memcpy(dev->netdev->dev_addr, node_id, sizeof(node_id));
+		return true;
+	}
+	return false;
 }
 
 static int rtl8150_set_mac_address(struct net_device *netdev, void *p)
@@ -909,21 +914,24 @@  static int rtl8150_probe(struct usb_interface *intf,
 		goto out1;
 	}
 	fill_skb_pool(dev);
-	set_ethernet_addr(dev);
-
+	if (!set_ethernet_addr(dev)) {
+		dev_err(&intf->dev, "couldn't set the ethernet address for the device\n");
+		goto out2;
+	}
 	usb_set_intfdata(intf, dev);
 	SET_NETDEV_DEV(netdev, &intf->dev);
 	if (register_netdev(netdev) != 0) {
 		dev_err(&intf->dev, "couldn't register the device\n");
-		goto out2;
+		goto out3;
 	}
 
 	dev_info(&intf->dev, "%s: rtl8150 is detected\n", netdev->name);
 
 	return 0;
 
-out2:
+out3:
 	usb_set_intfdata(intf, NULL);
+out2:
 	free_skb_pool(dev);
 out1:
 	free_all_urbs(dev);