[PATCH] rt2x00: reset reg earlier in rt2500usb_register_read

In the function rt2500usb_register_read(_lock), reg is uninitialized
in some situation. Then KMSAN reports uninit-value at its first memory
access. To fix this issue, initialize reg with zero in the function
rt2500usb_register_read and rt2500usb_register_read_lock

BUG: KMSAN: uninit-value in rt2500usb_init_eeprom rt2500usb.c:1443 [inline]
BUG: KMSAN: uninit-value in rt2500usb_probe_hw+0xb5e/0x22a0 rt2500usb.c:1757
CPU: 0 PID: 3369 Comm: kworker/0:2 Not tainted 5.3.0-rc7+ #0
Hardware name: Google Compute Engine
Workqueue: usb_hub_wq hub_event
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x191/0x1f0 lib/dump_stack.c:113
 kmsan_report+0x162/0x2d0 mm/kmsan/kmsan_report.c:109
 __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:294
 rt2500usb_init_eeprom wireless/ralink/rt2x00/rt2500usb.c:1443 [inline]
 rt2500usb_probe_hw+0xb5e/0x22a0 wireless/ralink/rt2x00/rt2500usb.c:1757
 rt2x00lib_probe_dev+0xba9/0x3260 wireless/ralink/rt2x00/rt2x00dev.c:1427
 rt2x00usb_probe+0x7ae/0xf60 wireless/ralink/rt2x00/rt2x00usb.c:842
 rt2500usb_probe+0x50/0x60 wireless/ralink/rt2x00/rt2500usb.c:1966
 ......

Local variable description: ----reg.i.i@rt2500usb_probe_hw
Variable was created at:
 rt2500usb_register_read wireless/ralink/rt2x00/rt2500usb.c:51 [inline]
 rt2500usb_init_eeprom wireless/ralink/rt2x00/rt2500usb.c:1440 [inline]
 rt2500usb_probe_hw+0x774/0x22a0 wireless/ralink/rt2x00/rt2500usb.c:1757
 rt2x00lib_probe_dev+0xba9/0x3260 wireless/ralink/rt2x00/rt2x00dev.c:1427

Signed-off-by: Dongliang Mu <redacted>
---
 drivers/net/wireless/ralink/rt2x00/rt2500usb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ralink/rt2x00/rt2500usb.c b/drivers/net/wireless/ralink/rt2x00/rt2500usb.c
index fce05fc88aaf..98567dc96415 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2500usb.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2500usb.c

@@ -47,7 +47,7 @@ MODULE_PARM_DESC(nohwcrypt, "Disable hardware encryption.");
 static u16 rt2500usb_register_read(struct rt2x00_dev *rt2x00dev,
 				   const unsigned int offset)
 {
-	__le16 reg;
+	__le16 reg = 0;
 	rt2x00usb_vendor_request_buff(rt2x00dev, USB_MULTI_READ,
 				      USB_VENDOR_REQUEST_IN, offset,
 				      &reg, sizeof(reg));

@@ -57,7 +57,7 @@ static u16 rt2500usb_register_read(struct rt2x00_dev *rt2x00dev,
 static u16 rt2500usb_register_read_lock(struct rt2x00_dev *rt2x00dev,
 					const unsigned int offset)
 {
-	__le16 reg;
+	__le16 reg = 0;
 	rt2x00usb_vendor_req_buff_lock(rt2x00dev, USB_MULTI_READ,
 				       USB_VENDOR_REQUEST_IN, offset,
 				       &reg, sizeof(reg), REGISTER_TIMEOUT);

-- 
2.25.1

On Thu, Jan 21, 2021 at 06:52:46PM +0800, Dongliang Mu wrote:

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
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/SubmittingPatches for what needs to be done
  here to properly describe this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot