[Xen-changelog] [qemu-xen stable-4.4] usb: check page select value while processing iTD

[patchbot@xxxxxxx]

commit d08f9e6bfc8d15d1ac6377e4cfe48e1f4ef4d932
Author:     Prasad J Pandit <pjp@xxxxxxxxxxxxxxxxx>
AuthorDate: Wed Jan 20 01:26:46 2016 +0530
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
CommitDate: Fri Feb 5 14:53:53 2016 +0000

    usb: check page select value while processing iTD
    
    While processing isochronous transfer descriptors(iTD), the page
    select(PG) field value could lead to an OOB read access. Add
    check to avoid it.
    
    Reported-by: Qinghao Tang <luodalongde@xxxxxxxxx>
    Signed-off-by: Prasad J Pandit <pjp@xxxxxxxxxxxxxxxxx>
    Message-id: 1453233406-12165-1-git-send-email-ppandit@xxxxxxxxxx
    Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
---
 hw/usb/hcd-ehci.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
index e9fb20c..30960f5 100644
--- a/hw/usb/hcd-ehci.c
+++ b/hw/usb/hcd-ehci.c
@@ -1472,21 +1472,23 @@ static int ehci_process_itd(EHCIState *ehci,
         if (itd->transact[i] & ITD_XACT_ACTIVE) {
             pg   = get_field(itd->transact[i], ITD_XACT_PGSEL);
             off  = itd->transact[i] & ITD_XACT_OFFSET_MASK;
-            ptr1 = (itd->bufptr[pg] & ITD_BUFPTR_MASK);
-            ptr2 = (itd->bufptr[pg+1] & ITD_BUFPTR_MASK);
             len  = get_field(itd->transact[i], ITD_XACT_LENGTH);
 
             if (len > max * mult) {
                 len = max * mult;
             }
-
-            if (len > BUFF_SIZE) {
+            if (len > BUFF_SIZE || pg > 6) {
                 return -1;
             }
 
+            ptr1 = (itd->bufptr[pg] & ITD_BUFPTR_MASK);
             qemu_sglist_init(&ehci->isgl, ehci->device, 2, ehci->as);
             if (off + len > 4096) {
                 /* transfer crosses page border */
+                if (pg == 6) {
+                    return -1;  /* avoid page pg + 1 */
+                }
+                ptr2 = (itd->bufptr[pg + 1] & ITD_BUFPTR_MASK);
                 uint32_t len2 = off + len - 4096;
                 uint32_t len1 = len - len2;
                 qemu_sglist_add(&ehci->isgl, ptr1 + off, len1);
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#stable-4.4

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