From: Thomas Huth <thuth@redhat.com>
The inner while loop in ohci_service_ed_list() could theoretically
loop forever if a malicious guest prepares a set of bad descriptors.
Add a check to the loop to avoid this situation.
Reported-by: Feifan Qian <bea1e@proton.me>
Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3781
Signed-off-by: Thomas Huth <thuth@redhat.com>
---
hw/usb/hcd-ohci.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/hw/usb/hcd-ohci.c b/hw/usb/hcd-ohci.c
index 40ebafb4dd9..c4a9741bd42 100644
--- a/hw/usb/hcd-ohci.c
+++ b/hw/usb/hcd-ohci.c
@@ -28,6 +28,7 @@
#include "qemu/osdep.h"
#include "hw/core/irq.h"
#include "qapi/error.h"
+#include "qemu/log.h"
#include "qemu/module.h"
#include "qemu/timer.h"
#include "hw/usb/usb.h"
@@ -1129,6 +1130,8 @@ static int ohci_service_ed_list(OHCIState *ohci, uint32_t head)
return 0;
}
for (cur = head; cur && link_cnt++ < ED_LINK_LIMIT; cur = next_ed) {
+ unsigned int ed_cnt = 0;
+
if (ohci_read_ed(ohci, cur, &ed)) {
trace_usb_ohci_ed_read_error(cur);
ohci_die(ohci);
@@ -1172,6 +1175,13 @@ static int ohci_service_ed_list(OHCIState *ohci, uint32_t head)
break;
}
}
+
+ if (ed_cnt++ > ED_LINK_LIMIT) {
+ qemu_log_mask(LOG_GUEST_ERROR,
+ "ohci: Too many endpoint descriptors in loop\n");
+ ohci_die(ohci);
+ return 0;
+ }
}
if (ohci_put_ed(ohci, cur, &ed)) {
--
2.55.0