Subject: [PATCH v2] ieee802154: atusb: fix uninit value in atusb_set_extended_addr

From: Pavel Skripkin <[email-masked]>
Date: Mon, 3 Jan 2022 15:09:25 +0300

Alexander reported a use of uninitialized value in
atusb_set_extended_addr(), that is caused by reading 0 bytes via
usb_control_msg().

Fix it by validating if the number of bytes transferred is actually
correct, since usb_control_msg() may read less bytes, than was requested
by caller.

Fail log:

BUG: KASAN: uninit-cmp in ieee802154_is_valid_extended_unicast_addr include/linux/ieee802154.h:310 [inline]
BUG: KASAN: uninit-cmp in atusb_set_extended_addr drivers/net/ieee802154/atusb.c:1000 [inline]
BUG: KASAN: uninit-cmp in atusb_probe.cold+0x29f/0x14db drivers/net/ieee802154/atusb.c:1056
Uninit value used in comparison: 311daa649a2003bd stack handle: 000000009a2003bd
 ieee802154_is_valid_extended_unicast_addr include/linux/ieee802154.h:310 [inline]
 atusb_set_extended_addr drivers/net/ieee802154/atusb.c:1000 [inline]
 atusb_probe.cold+0x29f/0x14db drivers/net/ieee802154/atusb.c:1056
 usb_probe_interface+0x314/0x7f0 drivers/usb/core/driver.c:396

Fixes: 7490b008d123 ("ieee802154: add support for atusb transceiver")
Reported-by: Alexander Potapenko <[email-masked]>
Signed-off-by: Pavel Skripkin <[email-masked]>
---

Changes in v2:
	- Reworked fix approach, since moving to new USB API is not
	  suitable for backporting to stable kernels

---
 drivers/net/ieee802154/atusb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ieee802154/atusb.c b/drivers/net/ieee802154/atusb.c
index 23ee0b14cbfa..e6cc816dd7a1 100644
--- a/drivers/net/ieee802154/atusb.c
+++ b/drivers/net/ieee802154/atusb.c
@@ -93,7 +93,9 @@ static int atusb_control_msg(struct atusb *atusb, unsigned int pipe,
 
 	ret = usb_control_msg(usb_dev, pipe, request, requesttype,
 			      value, index, data, size, timeout);
-	if (ret < 0) {
+	if (ret < size) {
+		ret = ret < 0 ? ret : -ENODATA;
+
 		atusb->err = ret;
 		dev_err(&usb_dev->dev,
 			"%s: req 0x%02x val 0x%x idx 0x%x, error %d\n",
-- 
2.34.1