[CVE-2017-7273][PATCH T] HID: hid-cypress: validate length of report

[Po-Hsu Lin]

From: Greg Kroah-Hartman <gregkh at linuxfoundation.org>

CVE-2017-7273

Make sure we have enough of a report structure to validate before
looking at it.

Reported-by: Benoit Camredon <benoit.camredon at airbus.com>
Tested-by: Benoit Camredon <benoit.camredon at airbus.com>
Cc: stable <stable at vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Jiri Kosina <jkosina at suse.cz>
(cherry picked from commit 1ebb71143758f45dc0fa76e2f48429e13b16d110)
Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
---
 drivers/hid/hid-cypress.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-cypress.c b/drivers/hid/hid-cypress.c
index c4ef3bc..e299576 100644
--- a/drivers/hid/hid-cypress.c
+++ b/drivers/hid/hid-cypress.c
@@ -39,6 +39,9 @@ static __u8 *cp_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 	if (!(quirks & CP_RDESC_SWAPPED_MIN_MAX))
 		return rdesc;
 
+	if (*rsize < 4)
+		return rdesc;
+
 	for (i = 0; i < *rsize - 4; i++)
 		if (rdesc[i] == 0x29 && rdesc[i + 2] == 0x19) {
 			__u8 tmp;
-- 
2.7.4