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From 95ed56939eb2eaa4e2f349fe6dcd13ca4edfd8fb Mon Sep 17 00:00:00 2001
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From: Li Qiang <liqiang6-s@360.cn>
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Date: Tue, 7 Feb 2017 02:23:33 -0800
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Subject: [PATCH] usb: ohci: limit the number of link eds
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The guest may builds an infinite loop with link eds. This patch
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limit the number of linked ed to avoid this.
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Signed-off-by: Li Qiang <liqiang6-s@360.cn>
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Message-id: 5899a02e.45ca240a.6c373.93c1@mx.google.com
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Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
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---
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hw/usb-ohci.c | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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diff --git a/hw/usb-ohci.c b/hw/usb-ohci.c
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index 2cba3e3..21c93e0 100644
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--- a/hw/usb-ohci.c
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+++ b/hw/usb-ohci.c
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@@ -42,6 +42,8 @@
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#define OHCI_MAX_PORTS 15
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+#define ED_LINK_LIMIT 4
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+
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static int64_t usb_frame_time;
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static int64_t usb_bit_time;
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@@ -1184,7 +1186,7 @@ static int ohci_service_ed_list(OHCIState *ohci, uint32_t head, int completion)
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uint32_t next_ed;
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uint32_t cur;
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int active;
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-
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+ uint32_t link_cnt = 0;
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active = 0;
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if (head == 0)
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@@ -1199,6 +1201,10 @@ static int ohci_service_ed_list(OHCIState *ohci, uint32_t head, int completion)
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next_ed = ed.next & OHCI_DPTR_MASK;
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+ if (++link_cnt > ED_LINK_LIMIT) {
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+ return 0;
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+ }
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+
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if ((ed.head & OHCI_ED_H) || (ed.flags & OHCI_ED_K)) {
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uint32_t addr;
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/* Cancel pending packets for ED that have been paused. */
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--
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1.8.3.1
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