[PULL 4/5] hw/usb/core: Avoid possible assert() in do_parameter() --> usb_packet_copy()

[Thomas Huth <thuth@redhat.com>]

From: Thomas Huth <thuth@redhat.com>

usb_packet_copy() uses assert(p->actual_length + bytes <= iov->size)
to make sure that there is enough space in the the iov. This assert()
can be triggered from do_parameter() if the guest programs the XHCI
in a weird way. Avoid the hard error by checking for the condition
in do_parameter() first and signalling a USB_RET_STALL to the guest,
just like it is done for another error condition here already some
lines earlier.

Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3746
Reported-by: Yunhe Wang <yunhewwww@163.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-ID: <20260721185140.247775-1-thuth@redhat.com>
---
 hw/usb/core.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/usb/core.c b/hw/usb/core.c
index d71204c5c80..43653c26cae 100644
--- a/hw/usb/core.c
+++ b/hw/usb/core.c
@@ -26,6 +26,7 @@
 #include "qemu/osdep.h"
 #include "hw/usb/usb.h"
 #include "qemu/iov.h"
+#include "qemu/log.h"
 #include "trace.h"
 
 void usb_pick_speed(USBPort *port)
@@ -288,6 +289,15 @@ static void do_parameter(USBDevice *s, USBPacket *p)
         p->status = USB_RET_STALL;
         return;
     }
+    if ((p->pid == USB_TOKEN_OUT || p->pid == USB_TOKEN_IN) &&
+        setup_len > p->iov.size) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "xhci: setup state param length %u > iov size %zu\n",
+                      setup_len, p->iov.size);
+        p->status = USB_RET_STALL;
+        return;
+    }
+
     s->setup_len = setup_len;
 
     if (p->pid == USB_TOKEN_OUT) {
-- 
2.55.0