From feb16ff29a13a4286389bb8b9d4f541aab9b84f1 Mon Sep 17 00:00:00 2001

From: Jon Maloy <jmaloy@redhat.com>

Date: Thu, 3 Sep 2020 15:27:13 -0400

Subject: [PATCH] usb: fix setup_len init (CVE-2020-14364)

RH-Author: Jon Maloy <jmaloy@redhat.com>

Message-id: <20200903152713.1420531-2-jmaloy@redhat.com>

Patchwork-id: 98271

O-Subject: [RHEL-8.3.0 qemu-kvm PATCH 1/1] usb: fix setup_len init (CVE-2020-14364)

Bugzilla: 1869710

RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

RH-Acked-by: Thomas Huth <thuth@redhat.com>

RH-Acked-by: Gerd Hoffmann <kraxel@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: Danilo C. L. de Paula <ddepaula@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 5abd128b6b..5234dcc73f 100644

--- a/hw/usb/core.c

+++ b/hw/usb/core.c

@@ -129,6 +129,7 @@ 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;

@@ -138,14 +139,15 @@ 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];

@@ -259,26 +261,28 @@ 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);

-- 

2.27.0