[app-emulation/qemu] sync with tree

app-emulation/qemu/files/qemu-2.5.0-CVE-2016-1981.patch

@@ -0,0 +1,98 @@
+From dd793a74882477ca38d49e191110c17dfee51dcc Mon Sep 17 00:00:00 2001
+From: Laszlo Ersek <lersek@redhat.com>
+Date: Tue, 19 Jan 2016 14:17:20 +0100
+Subject: [PATCH] e1000: eliminate infinite loops on out-of-bounds transfer
+ start
+
+The start_xmit() and e1000_receive_iov() functions implement DMA transfers
+iterating over a set of descriptors that the guest's e1000 driver
+prepares:
+
+- the TDLEN and RDLEN registers store the total size of the descriptor
+  area,
+
+- while the TDH and RDH registers store the offset (in whole tx / rx
+  descriptors) into the area where the transfer is supposed to start.
+
+Each time a descriptor is processed, the TDH and RDH register is bumped
+(as appropriate for the transfer direction).
+
+QEMU already contains logic to deal with bogus transfers submitted by the
+guest:
+
+- Normally, the transmit case wants to increase TDH from its initial value
+  to TDT. (TDT is allowed to be numerically smaller than the initial TDH
+  value; wrapping at or above TDLEN bytes to zero is normal.) The failsafe
+  that QEMU currently has here is a check against reaching the original
+  TDH value again -- a complete wraparound, which should never happen.
+
+- In the receive case RDH is increased from its initial value until
+  "total_size" bytes have been received; preferably in a single step, or
+  in "s->rxbuf_size" byte steps, if the latter is smaller. However, null
+  RX descriptors are skipped without receiving data, while RDH is
+  incremented just the same. QEMU tries to prevent an infinite loop
+  (processing only null RX descriptors) by detecting whether RDH assumes
+  its original value during the loop. (Again, wrapping from RDLEN to 0 is
+  normal.)
+
+What both directions miss is that the guest could program TDLEN and RDLEN
+so low, and the initial TDH and RDH so high, that these registers will
+immediately be truncated to zero, and then never reassume their initial
+values in the loop -- a full wraparound will never occur.
+
+The condition that expresses this is:
+
+  xdh_start >= s->mac_reg[XDLEN] / sizeof(desc)
+
+i.e., TDH or RDH start out after the last whole rx or tx descriptor that
+fits into the TDLEN or RDLEN sized area.
+
+This condition could be checked before we enter the loops, but
+pci_dma_read() / pci_dma_write() knows how to fill in buffers safely for
+bogus DMA addresses, so we just extend the existing failsafes with the
+above condition.
+
+This is CVE-2016-1981.
+
+Cc: "Michael S. Tsirkin" <mst@redhat.com>
+Cc: Petr Matousek <pmatouse@redhat.com>
+Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
+Cc: Prasad Pandit <ppandit@redhat.com>
+Cc: Michael Roth <mdroth@linux.vnet.ibm.com>
+Cc: Jason Wang <jasowang@redhat.com>
+Cc: qemu-stable@nongnu.org
+RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1296044
+Signed-off-by: Laszlo Ersek <lersek@redhat.com>
+Reviewed-by: Jason Wang <jasowang@redhat.com>
+Signed-off-by: Jason Wang <jasowang@redhat.com>
+---
+ hw/net/e1000.c | 6 ++++--
+ 1 file changed, 4 insertions(+), 2 deletions(-)
+
+diff --git a/hw/net/e1000.c b/hw/net/e1000.c
+index 4eda7a3..0387fa0 100644
+--- a/hw/net/e1000.c
++++ b/hw/net/e1000.c
+@@ -909,7 +909,8 @@ start_xmit(E1000State *s)
+          * bogus values to TDT/TDLEN.
+          * there's nothing too intelligent we could do about this.
+          */
+-        if (s->mac_reg[TDH] == tdh_start) {
++        if (s->mac_reg[TDH] == tdh_start ||
++            tdh_start >= s->mac_reg[TDLEN] / sizeof(desc)) {
+             DBGOUT(TXERR, "TDH wraparound @%x, TDT %x, TDLEN %x\n",
+                    tdh_start, s->mac_reg[TDT], s->mac_reg[TDLEN]);
+             break;
+@@ -1166,7 +1167,8 @@ e1000_receive_iov(NetClientState *nc, const struct iovec *iov, int iovcnt)
+         if (++s->mac_reg[RDH] * sizeof(desc) >= s->mac_reg[RDLEN])
+             s->mac_reg[RDH] = 0;
+         /* see comment in start_xmit; same here */
+-        if (s->mac_reg[RDH] == rdh_start) {
++        if (s->mac_reg[RDH] == rdh_start ||
++            rdh_start >= s->mac_reg[RDLEN] / sizeof(desc)) {
+             DBGOUT(RXERR, "RDH wraparound @%x, RDT %x, RDLEN %x\n",
+                    rdh_start, s->mac_reg[RDT], s->mac_reg[RDLEN]);
+             set_ics(s, 0, E1000_ICS_RXO);
+-- 
+2.7.4
+