[PATCH] xhci: check return value from usb_packet_map

[P J P]

From: Prasad J Pandit <pjp@fedoraproject.org>

While setting up a packet in xhci_setup_packet() routine,
usb_packet_map() may return an error. Check this return value
before further processing the packet, to avoid use-after-free
issue.

 -> https://ruhr-uni-bochum.sciebo.de/s/NNWP2GfwzYKeKwE?path=%2Fxhci_uaf_2
  #0  __interceptor_free (/lib64/libasan.so.6+0xb0307)
  #1  qemu_vfree ../util/oslib-posix.c:247
  #2  address_space_unmap ../exec.c:3635
  #3  dma_memory_unmap ../include/sysemu/dma.h:145
  #4  usb_packet_unmap ../hw/usb/libhw.c:65
  #5  usb_packet_map ../hw/usb/libhw.c:54
  #6  xhci_setup_packet ../hw/usb/hcd-xhci.c:1618
  #7  xhci_fire_ctl_transfer ../hw/usb/hcd-xhci.c:1722
  #8  xhci_kick_epctx ../hw/usb/hcd-xhci.c:1991
  #9  xhci_kick_ep ../hw/usb/hcd-xhci.c:1861
  #10 xhci_doorbell_write ../hw/usb/hcd-xhci.c:3162
  ...

Reported-by: Ruhr-University <bugs-syssec@rub.de>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/usb/hcd-xhci.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c
index 67a18fe2b6..848e7e935f 100644
--- a/hw/usb/hcd-xhci.c
+++ b/hw/usb/hcd-xhci.c
@@ -1615,7 +1615,14 @@ static int xhci_setup_packet(XHCITransfer *xfer)
     xhci_xfer_create_sgl(xfer, dir == USB_TOKEN_IN); /* Also sets int_req */
     usb_packet_setup(&xfer->packet, dir, ep, xfer->streamid,
                      xfer->trbs[0].addr, false, xfer->int_req);
-    usb_packet_map(&xfer->packet, &xfer->sgl);
+    if (usb_packet_map(&xfer->packet, &xfer->sgl) < 0) {
+        DPRINTF("xhci: setup packet failed: pid: 0x%x addr %d ep %d\n",
+                xfer->packet.pid, ep->dev->addr, ep->nr);
+        usb_packet_cleanup(&xfer->packet);
+        qemu_sglist_destroy(&xfer->sgl);
+        return -1;
+    }
+
     DPRINTF("xhci: setup packet pid 0x%x addr %d ep %d\n",
             xfer->packet.pid, ep->dev->addr, ep->nr);
     return 0;
-- 
2.26.2