On 29/09/20 2:17 pm, Petko Manolov wrote:

On 20-09-29 13:50:28, Anant Thazhemadam wrote:

quoted

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 <redacted>
---
 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