From 9330e486e884f1757d6920a25c6cc491eedad0d0 Mon Sep 17 00:00:00 2001
From: Jon Maloy <jmaloy@redhat.com>
Date: Fri, 4 Sep 2020 16:09:13 -0400
Subject: [PATCH 3/3] usb: fix setup_len init (CVE-2020-14364)

RH-Author: Jon Maloy <jmaloy@redhat.com>
Message-id: <20200904160913.87759-3-jmaloy@redhat.com>
Patchwork-id: 98291
O-Subject: [RHEL-7.9 qemu-kvm PATCH 2/2] usb: fix setup_len init (CVE-2020-14364)
Bugzilla: 1869693
RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
RH-Acked-by: Gerd Hoffmann <kraxel@redhat.com>
RH-Acked-by: Thomas Huth <thuth@redhat.com>

From: Gerd Hoffmann <kraxel@redhat.com>

Store calculated setup_len in a local variable, verify it, and only
write it to the struct (USBDevice->setup_len) in case it passed the
sanity checks.

This prevents other code (do_token_{in,out} functions specifically)
from working with invalid USBDevice->setup_len values and overrunning
the USBDevice->setup_buf[] buffer.

Fixes: CVE-2020-14364
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Tested-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Li Qiang <liq3ea@gmail.com>
Message-id: 20200825053636.29648-1-kraxel@redhat.com
(cherry picked from commit b946434f2659a182afc17e155be6791ebfb302eb)
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Jon Maloy <jmaloy.redhat.com>
---
 hw/usb/core.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/hw/usb/core.c b/hw/usb/core.c
index f0201e30b4..f0038e44ae 100644
--- a/hw/usb/core.c
+++ b/hw/usb/core.c
@@ -121,6 +121,7 @@ void usb_wakeup(USBEndpoint *ep, unsigned int stream)
 static void do_token_setup(USBDevice *s, USBPacket *p)
 {
     int request, value, index;
+    unsigned int setup_len;
 
     if (p->iov.size != 8) {
         p->status = USB_RET_STALL;
@@ -130,14 +131,15 @@ static void do_token_setup(USBDevice *s, USBPacket *p)
     usb_packet_copy(p, s->setup_buf, p->iov.size);
     s->setup_index = 0;
     p->actual_length = 0;
-    s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
-    if (s->setup_len > sizeof(s->data_buf)) {
+    setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
+    if (setup_len > sizeof(s->data_buf)) {
         fprintf(stderr,
                 "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
-                s->setup_len, sizeof(s->data_buf));
+                setup_len, sizeof(s->data_buf));
         p->status = USB_RET_STALL;
         return;
     }
+    s->setup_len = setup_len;
 
     request = (s->setup_buf[0] << 8) | s->setup_buf[1];
     value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
@@ -251,26 +253,28 @@ static void do_token_out(USBDevice *s, USBPacket *p)
 static void do_parameter(USBDevice *s, USBPacket *p)
 {
     int i, request, value, index;
+    unsigned int setup_len;
 
     for (i = 0; i < 8; i++) {
         s->setup_buf[i] = p->parameter >> (i*8);
     }
 
     s->setup_state = SETUP_STATE_PARAM;
-    s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
     s->setup_index = 0;
 
     request = (s->setup_buf[0] << 8) | s->setup_buf[1];
     value   = (s->setup_buf[3] << 8) | s->setup_buf[2];
     index   = (s->setup_buf[5] << 8) | s->setup_buf[4];
 
-    if (s->setup_len > sizeof(s->data_buf)) {
+    setup_len = (s->setup_buf[7] << 8) | s->setup_buf[6];
+    if (setup_len > sizeof(s->data_buf)) {
         fprintf(stderr,
                 "usb_generic_handle_packet: ctrl buffer too small (%d > %zu)\n",
-                s->setup_len, sizeof(s->data_buf));
+                setup_len, sizeof(s->data_buf));
         p->status = USB_RET_STALL;
         return;
     }
+    s->setup_len = setup_len;
 
     if (p->pid == USB_TOKEN_OUT) {
         usb_packet_copy(p, s->data_buf, s->setup_len);
-- 
2.18.2