HID: hid-steam: Better handling of serial number length

The second byte of the GET_STRING_ATTRIB report is a length, so we should set
the size of the buffer to be the size we're actually requesting, and only
reject the reply if the length out is nonsensical.

Signed-off-by: Vicki Pfau <vi@endrift.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

diff --git a/drivers/hid/hid-steam.c b/drivers/hid/hid-steam.c
index 4f5c647f04dd0c92b948161932d0013cea7d49b4..a0ed8812e7ead56d3c2c39176cc8fb8c369ddbb2 100644 (file)
--- a/drivers/hid/hid-steam.c
+++ b/drivers/hid/hid-steam.c
@@ -274,7 +274,7 @@ enum {
 };
 
 /* Other random constants */
-#define STEAM_SERIAL_LEN 10
+#define STEAM_SERIAL_LEN 0x15
 
 struct steam_device {
        struct list_head list;
@@ -421,10 +421,10 @@ static int steam_get_serial(struct steam_device *steam)
 {
        /*
         * Send: 0xae 0x15 0x01
-        * Recv: 0xae 0x15 0x01 serialnumber (10 chars)
+        * Recv: 0xae 0x15 0x01 serialnumber
         */
        int ret = 0;
-       u8 cmd[] = {ID_GET_STRING_ATTRIBUTE, 0x15, ATTRIB_STR_UNIT_SERIAL};
+       u8 cmd[] = {ID_GET_STRING_ATTRIBUTE, sizeof(steam->serial_no), ATTRIB_STR_UNIT_SERIAL};
        u8 reply[3 + STEAM_SERIAL_LEN + 1];
 
        mutex_lock(&steam->report_mutex);
@@ -434,12 +434,13 @@ static int steam_get_serial(struct steam_device *steam)
        ret = steam_recv_report(steam, reply, sizeof(reply));
        if (ret < 0)
                goto out;
-       if (reply[0] != ID_GET_STRING_ATTRIBUTE || reply[1] != 0x15 || reply[2] != ATTRIB_STR_UNIT_SERIAL) {
+       if (reply[0] != ID_GET_STRING_ATTRIBUTE || reply[1] < 1 ||
+           reply[1] > sizeof(steam->serial_no) || reply[2] != ATTRIB_STR_UNIT_SERIAL) {
                ret = -EIO;
                goto out;
        }
        reply[3 + STEAM_SERIAL_LEN] = 0;
-       strscpy(steam->serial_no, reply + 3, sizeof(steam->serial_no));
+       strscpy(steam->serial_no, reply + 3, reply[1]);
 out:
        mutex_unlock(&steam->report_mutex);
        return ret;