[qemu-xen stable-4.12] usb: fix setup_len init (CVE-2020-14364)

[patchbot@xxxxxxx]

commit 92a78636a51611475f711637c44cafbda3ef9859
Author:     Gerd Hoffmann <kraxel@xxxxxxxxxx>
AuthorDate: Tue Aug 25 07:36:36 2020 +0200
Commit:     Anthony PERARD <anthony.perard@xxxxxxxxxx>
CommitDate: Fri Nov 6 15:37:12 2020 +0000

    usb: fix setup_len init (CVE-2020-14364)
    
    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@xxxxxxxxxx>
    Tested-by: Gonglei <arei.gonglei@xxxxxxxxxx>
    Reviewed-by: Li Qiang <liq3ea@xxxxxxxxx>
    Message-id: 20200825053636.29648-1-kraxel@xxxxxxxxxx
    (cherry picked from commit b946434f2659a182afc17e155be6791ebfb302eb)
---
 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 241ae66b15..c060a83656 100644
--- a/hw/usb/core.c
+++ b/hw/usb/core.c
@@ -130,6 +130,7 @@ 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;
@@ -139,14 +140,15 @@ 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];
@@ -260,26 +262,28 @@ 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);
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#stable-4.12