[PATCH 3.16 223/305] HID: hiddev: validate num_values for HIDIOCGUSAGES, HIDIOCSUSAGES commands

[Ben Hutchings]

3.16.37-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Scott Bauer <sba...@plzdonthack.me>

commit 93a2001bdfd5376c3dc2158653034c20392d15c5 upstream.

This patch validates the num_values parameter from userland during the
HIDIOCGUSAGES and HIDIOCSUSAGES commands. Previously, if the report id was set
to HID_REPORT_ID_UNKNOWN, we would fail to validate the num_values parameter
leading to a heap overflow.

Signed-off-by: Scott Bauer <sba...@plzdonthack.me>
Signed-off-by: Jiri Kosina <jkos...@suse.cz>
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 drivers/hid/usbhid/hiddev.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -516,13 +516,13 @@ static noinline int hiddev_ioctl_usage(s
                                        goto inval;
                        } else if (uref->usage_index >= field->report_count)
                                goto inval;
-
-                       else if ((cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) 
&&
-                                (uref_multi->num_values > HID_MAX_MULTI_USAGES 
||
-                                 uref->usage_index + uref_multi->num_values > 
field->report_count))
-                               goto inval;
                }
 
+               if ((cmd == HIDIOCGUSAGES || cmd == HIDIOCSUSAGES) &&
+                   (uref_multi->num_values > HID_MAX_MULTI_USAGES ||
+                    uref->usage_index + uref_multi->num_values > 
field->report_count))
+                       goto inval;
+
                switch (cmd) {
                case HIDIOCGUSAGE:
                        uref->value = field->value[uref->usage_index];