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From 156a2e4dbffa85997636a7a39ef12da6f1b40254 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Mon, 14 Dec 2015 09:21:23 +0100
Subject: ehci: make idt processing more robust
Bug-Debian: http://bugs.debian.org/808144
Make ehci_process_itd return an error in case we didn't do any actual
iso transfer because we've found no active transaction. That'll avoid
ehci happily run in circles forever if the guest builds a loop out of
idts.
This is CVE-2015-8558.
Cc: qemu-stable@nongnu.org
Reported-by: Qinghao Tang <luodalongde@gmail.com>
Tested-by: P J P <ppandit@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
hw/usb/hcd-ehci.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
index a511b4e..78d932f 100644
--- a/hw/usb/hcd-ehci.c
+++ b/hw/usb/hcd-ehci.c
@@ -1425,7 +1425,7 @@ static int ehci_process_itd(EHCIState *ehci,
USBDevice *dev;
USBEndpoint *ep;
int ret;
- uint32_t i, len, pid, dir, devaddr, endp;
+ uint32_t i, len, pid, dir, devaddr, endp, xfers = 0;
uint32_t pg, off, ptr1, ptr2, max, mult;
dir =(itd->bufptr[1] & ITD_BUFPTR_DIRECTION);
@@ -1513,9 +1513,10 @@ static int ehci_process_itd(EHCIState *ehci,
ehci_record_interrupt(ehci, USBSTS_INT);
}
itd->transact[i] &= ~ITD_XACT_ACTIVE;
+ xfers++;
}
}
- return 0;
+ return xfers ? 0 : -1;
}
/* This state is the entry point for asynchronous schedule
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