From 05f43d44e4bc26611ce25fd7d726e483f73363ce Mon Sep 17 00:00:00 2001 From: Gerd Hoffmann 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 Tested-by: P J P Signed-off-by: Gerd Hoffmann Message-id: 1476096382-7981-1-git-send-email-kraxel@redhat.com --- hw/usb/hcd-xhci.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c index 726435c..ee4fa48 100644 --- a/hw/usb/hcd-xhci.c +++ b/hw/usb/hcd-xhci.c @@ -54,6 +54,8 @@ * 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) @@ -1000,6 +1002,7 @@ 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; @@ -1026,6 +1029,9 @@ 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; @@ -1043,6 +1049,7 @@ 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; @@ -1058,6 +1065,9 @@ 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; -- 1.7.0.4