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

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  [PATCH 3.16 223/305] HID: hiddev: validate num_values for  HIDIOCGUSAGES, HIDIOCSUSAGES commands Ben Hutchings <ben@decadent.org.uk> - 2016-08-14 14:00 +0200

#1462076 — [PATCH 3.16 223/305] HID: hiddev: validate num_values for HIDIOCGUSAGES, HIDIOCSUSAGES commands

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

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

From: Scott Bauer <sbauer@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 <sbauer@plzdonthack.me>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Ben Hutchings <ben@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];

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