From: Gerd Hoffmann Date: Mon, 18 Apr 2016 09:11:38 +0200 Subject: [PATCH] ehci: apply limit to iTD/sidt descriptors MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Commit "156a2e4 ehci: make idt processing more robust" tries to avoid a DoS by the guest (create a circular iTD queue and let qemu ehci emulation run in circles forever). Unfortunately this has two problems: First it misses the case of siTDs, and second it reportedly breaks FreeBSD. So lets go for a different approach: just count the number of iTDs and siTDs we have seen per frame and apply a limit. That should really catch all cases now. Reported-by: 杜少博 Signed-off-by: Gerd Hoffmann (cherry picked from commit 1ae3f2f178087711f9591350abad133525ba93f2) --- hw/usb/hcd-ehci.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c index c40013e..b75488b 100644 --- a/hw/usb/hcd-ehci.c +++ b/hw/usb/hcd-ehci.c @@ -2003,6 +2003,7 @@ static int ehci_state_writeback(EHCIQueue *q) static void ehci_advance_state(EHCIState *ehci, int async) { EHCIQueue *q = NULL; + int itd_count = 0; int again; do { @@ -2027,10 +2028,12 @@ static void ehci_advance_state(EHCIState *ehci, int async) case EST_FETCHITD: again = ehci_state_fetchitd(ehci, async); + itd_count++; break; case EST_FETCHSITD: again = ehci_state_fetchsitd(ehci, async); + itd_count++; break; case EST_ADVANCEQUEUE: @@ -2079,7 +2082,8 @@ static void ehci_advance_state(EHCIState *ehci, int async) break; } - if (again < 0) { + if (again < 0 || itd_count > 16) { + /* TODO: notify guest (raise HSE irq?) */ fprintf(stderr, "processing error - resetting ehci HC\n"); ehci_reset(ehci); again = 0;