[PATCH 4.4 123/268] watchdog: f71808e_wdt: Fix magic close handling

From: Greg Kroah-Hartman
Date: Mon May 28 2018 - 11:30:22 EST


4.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Igor Pylypiv <igor.pylypiv@xxxxxxxxx>

[ Upstream commit 7bd3e7b743956afbec30fb525bc3c5e22e3d475c ]

Watchdog close is "expected" when any byte is 'V' not just the last one.
Writing "V" to the device fails because the last byte is the end of string.

$ echo V > /dev/watchdog
f71808e_wdt: Unexpected close, not stopping watchdog!

Signed-off-by: Igor Pylypiv <igor.pylypiv@xxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Wim Van Sebroeck <wim@xxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/watchdog/f71808e_wdt.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/watchdog/f71808e_wdt.c
+++ b/drivers/watchdog/f71808e_wdt.c
@@ -520,7 +520,8 @@ static ssize_t watchdog_write(struct fil
char c;
if (get_user(c, buf + i))
return -EFAULT;
- expect_close = (c == 'V');
+ if (c == 'V')
+ expect_close = true;
}

/* Properly order writes across fork()ed processes */