watchdog: jz4740_wdt - fix magic character checking

When writing to /dev/watchdog all characters should be checked
for the magic character 'V'.

Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

1 files changed, 11 insertions, 4 deletions

diff --git a/drivers/watchdog/jz4740_wdt.c b/drivers/watchdog/jz4740_wdt.c
index 935562322b38..684ba01fb540 100644
--- a/drivers/watchdog/jz4740_wdt.c
+++ b/drivers/watchdog/jz4740_wdt.c
@@ -130,11 +130,18 @@ static ssize_t jz4740_wdt_write(struct file *file, const char *data,
                 size_t len, loff_t *ppos)
 {
         if (len) {
-                if (data[len-1] == 'V')
-                        set_bit(WDT_OK_TO_CLOSE, &jz4740_wdt.status);
-                else
-                        clear_bit(WDT_OK_TO_CLOSE, &jz4740_wdt.status);
+                size_t i;
 
+                clear_bit(WDT_OK_TO_CLOSE, &jz4740_wdt.status);
+                for (i = 0; i != len; i++) {
+                        char c;
+
+                        if (get_user(c, data + i))
+                                return -EFAULT;
+
+                        if (c == 'V')
+                                set_bit(WDT_OK_TO_CLOSE, &jz4740_wdt.status);
+                }
                 jz4740_wdt_service();
         }