File 0073-xhci-limit-the-number-of-link-trbs-.patch of Package qemu.3505

From ff89e14467a845867c1bc9d4e2424c07b7679633 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Mon, 10 Oct 2016 12:46:22 +0200
Subject: [PATCH] xhci: limit the number of link trbs we are willing to process

Needed to avoid we run in circles forever in case the guest builds
an endless loop with link trbs.

Reported-by: Li Qiang <liqiang6-s@360.cn>
Tested-by: P J P <ppandit@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 1476096382-7981-1-git-send-email-kraxel@redhat.com
(cherry picked from commit 05f43d44e4bc26611ce25fd7d726e483f73363ce)
[BR: CVE-2016-8576 BSC#1003878]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 hw/usb/hcd-xhci.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c
index 510a3e1..4e9dea5 100644
--- a/hw/usb/hcd-xhci.c
+++ b/hw/usb/hcd-xhci.c
@@ -53,6 +53,8 @@
  * to the specs when it gets them */
 #define ER_FULL_HACK
 
+#define TRB_LINK_LIMIT  4
+
 #define LEN_CAP         0x40
 #define LEN_OPER        (0x400 + 0x10 * MAXPORTS)
 #define LEN_RUNTIME     ((MAXINTRS + 1) * 0x20)
@@ -999,6 +1001,7 @@ static TRBType xhci_ring_fetch(XHCIState *xhci, XHCIRing *ring, XHCITRB *trb,
                                dma_addr_t *addr)
 {
     PCIDevice *pci_dev = PCI_DEVICE(xhci);
+    uint32_t link_cnt = 0;
 
     while (1) {
         TRBType type;
@@ -1025,6 +1028,9 @@ static TRBType xhci_ring_fetch(XHCIState *xhci, XHCIRing *ring, XHCITRB *trb,
             ring->dequeue += TRB_SIZE;
             return type;
         } else {
+            if (++link_cnt > TRB_LINK_LIMIT) {
+                return 0;
+            }
             ring->dequeue = xhci_mask64(trb->parameter);
             if (trb->control & TRB_LK_TC) {
                 ring->ccs = !ring->ccs;
@@ -1042,6 +1048,7 @@ static int xhci_ring_chain_length(XHCIState *xhci, const XHCIRing *ring)
     bool ccs = ring->ccs;
     /* hack to bundle together the two/three TDs that make a setup transfer */
     bool control_td_set = 0;
+    uint32_t link_cnt = 0;
 
     while (1) {
         TRBType type;
@@ -1057,6 +1064,9 @@ static int xhci_ring_chain_length(XHCIState *xhci, const XHCIRing *ring)
         type = TRB_TYPE(trb);
 
         if (type == TR_LINK) {
+            if (++link_cnt > TRB_LINK_LIMIT) {
+                return -length;
+            }
             dequeue = xhci_mask64(trb.parameter);
             if (trb.control & TRB_LK_TC) {
                 ccs = !ccs;