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Subject[PATCH v2] watchdog: pcwd_usb: Fix attempting to access uninitialized memory
Date
The stack variable msb and lsb may be used uninitialized in function
usb_pcwd_get_temperature and usb_pcwd_get_timeleft when usb card no response.

The build waring is:
drivers/watchdog/pcwd_usb.c:336:22: error: ‘lsb’ is used uninitialized in this function [-Werror=uninitialized]
*temperature = (lsb * 9 / 5) + 32;
~~~~^~~
drivers/watchdog/pcwd_usb.c:328:21: note: ‘lsb’ was declared here
unsigned char msb, lsb;
^~~
cc1: all warnings being treated as errors
scripts/Makefile.build:250: recipe for target 'drivers/watchdog/pcwd_usb.o' failed
make[3]: *** [drivers/watchdog/pcwd_usb.o] Error 1

Fixes: b7e04f8c61a4 ("mv watchdog tree under drivers")
Signed-off-by: Li Hua <hucool.lihua@huawei.com>
---
v1 -> v2: just initialize lsb and msb with 0, but returning -EFAULT
---
drivers/watchdog/pcwd_usb.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/pcwd_usb.c b/drivers/watchdog/pcwd_usb.c
index 1bdaf17c1d38..8202f0a6b093 100644
--- a/drivers/watchdog/pcwd_usb.c
+++ b/drivers/watchdog/pcwd_usb.c
@@ -325,7 +325,8 @@ static int usb_pcwd_set_heartbeat(struct usb_pcwd_private *usb_pcwd, int t)
static int usb_pcwd_get_temperature(struct usb_pcwd_private *usb_pcwd,
int *temperature)
{
- unsigned char msb, lsb;
+ unsigned char msb = 0x00;
+ unsigned char lsb = 0x00;

usb_pcwd_send_command(usb_pcwd, CMD_READ_TEMP, &msb, &lsb);

@@ -341,7 +342,8 @@ static int usb_pcwd_get_temperature(struct usb_pcwd_private *usb_pcwd,
static int usb_pcwd_get_timeleft(struct usb_pcwd_private *usb_pcwd,
int *time_left)
{
- unsigned char msb, lsb;
+ unsigned char msb = 0x00;
+ unsigned char lsb = 0x00;

/* Read the time that's left before rebooting */
/* Note: if the board is not yet armed then we will read 0xFFFF */
--
2.17.1
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