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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@redhat.com>
Tested-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Li Qiang <liq3ea@gmail.com>
Message-id: 20200825053636.29648-1-kraxel@redhat.com
master
Gerd Hoffmann 2020-08-25 07:36:36 +02:00
parent 202d69a715
commit b946434f26
1 changed files with 10 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
hw/usb/core.c
View File

@ -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);