test_firmware: Use correct snprintf() limit

commit bd17cc5a20ae9aaa3ed775f360b75ff93cd66a1d upstream.

The limit here is supposed to be how much of the page is left, but it's
just using PAGE_SIZE as the limit.

The other thing to remember is that snprintf() returns the number of
bytes which would have been copied if we had had enough room.  So that
means that if we run out of space then this code would end up passing a
negative value as the limit and the kernel would print an error message.
I have change the code to use scnprintf() which returns the number of
bytes that were successfully printed (not counting the NUL terminator).

Fixes: c92316bf8e94 ("test_firmware: add batched firmware tests")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/lib/test_firmware.c b/lib/test_firmware.c
index 7cab9a9869ace92900ec58aabffa175d2249296d..fd48a15a0710c7c28a0e6fd7b2b7c4ad89a5312d 100644 (file)
--- a/lib/test_firmware.c
+++ b/lib/test_firmware.c
@@ -223,30 +223,30 @@ static ssize_t config_show(struct device *dev,
 
        mutex_lock(&test_fw_mutex);
 
-       len += snprintf(buf, PAGE_SIZE,
+       len += scnprintf(buf, PAGE_SIZE - len,
                        "Custom trigger configuration for: %s\n",
                        dev_name(dev));
 
        if (test_fw_config->name)
-               len += snprintf(buf+len, PAGE_SIZE,
+               len += scnprintf(buf+len, PAGE_SIZE - len,
                                "name:\t%s\n",
                                test_fw_config->name);
        else
-               len += snprintf(buf+len, PAGE_SIZE,
+               len += scnprintf(buf+len, PAGE_SIZE - len,
                                "name:\tEMTPY\n");
 
-       len += snprintf(buf+len, PAGE_SIZE,
+       len += scnprintf(buf+len, PAGE_SIZE - len,
                        "num_requests:\t%u\n", test_fw_config->num_requests);
 
-       len += snprintf(buf+len, PAGE_SIZE,
+       len += scnprintf(buf+len, PAGE_SIZE - len,
                        "send_uevent:\t\t%s\n",
                        test_fw_config->send_uevent ?
                        "FW_ACTION_HOTPLUG" :
                        "FW_ACTION_NOHOTPLUG");
-       len += snprintf(buf+len, PAGE_SIZE,
+       len += scnprintf(buf+len, PAGE_SIZE - len,
                        "sync_direct:\t\t%s\n",
                        test_fw_config->sync_direct ? "true" : "false");
-       len += snprintf(buf+len, PAGE_SIZE,
+       len += scnprintf(buf+len, PAGE_SIZE - len,
                        "read_fw_idx:\t%u\n", test_fw_config->read_fw_idx);
 
        mutex_unlock(&test_fw_mutex);