xen/CVE-2015-8345-qemut-eepro100-infinite-loop-fix.patch

References: bsc#956832 CVE-2015-8345

Subject: eepro100: Prevent two endless loops
From: Stefan Weil sw@weilnetz.de Fri Nov 20 08:42:33 2015 +0100
Date: Fri Nov 27 10:39:55 2015 +0800:
Git: 00837731d254908a841d69298a4f9f077babaf24

http://lists.nongnu.org/archive/html/qemu-devel/2015-11/msg04592.html
shows an example how an endless loop in function action_command can
be achieved.

During my code review, I noticed a 2nd case which can result in an
endless loop.

Reported-by: Qinghao Tang <luodalongde@gmail.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Signed-off-by: Jason Wang <jasowang@redhat.com>

Index: xen-4.6.0-testing/tools/qemu-xen-traditional-dir-remote/hw/eepro100.c
===================================================================
--- xen-4.6.0-testing.orig/tools/qemu-xen-traditional-dir-remote/hw/eepro100.c
+++ xen-4.6.0-testing/tools/qemu-xen-traditional-dir-remote/hw/eepro100.c
@@ -657,6 +657,10 @@ static void eepro100_cu_command(EEPRO100
 {
     eepro100_tx_t tx;
     uint32_t cb_address;
+    /* The loop below won't stop if it gets special handcrafted data.
+       Therefore we limit the number of iterations. */
+    unsigned max_loop_count = 16;
+
     switch (val) {
     case CU_NOP:
         /* No operation. */
@@ -685,6 +689,13 @@ static void eepro100_cu_command(EEPRO100
         bool bit_nc = ((command & 0x0010) != 0);
         //~ bool bit_sf = ((command & 0x0008) != 0);
         uint16_t cmd = command & 0x0007;
+
+        if (max_loop_count-- == 0) {
+            /* Prevent an endless loop. (see goto next_command) */
+            logout("loop in %s:%u\n", __FILE__, __LINE__);
+            break;
+        }
+
         s->cu_offset = le32_to_cpu(tx.link);
         switch (cmd) {
         case CmdNOp:
@@ -726,6 +737,11 @@ static void eepro100_cu_command(EEPRO100
                 uint32_t tx_buffer_address = ldl_phys(tbd_address);
                 uint16_t tx_buffer_size = lduw_phys(tbd_address + 4);
                 //~ uint16_t tx_buffer_el = lduw_phys(tbd_address + 6);
+                if (tx_buffer_size == 0) {
+                    /* Prevent an endless loop. */
+                    logout("loop in %s:%u\n", __FILE__, __LINE__);
+                    break;
+                }
                 tbd_address += 8;
                 logout
                     ("TBD (simplified mode): buffer address 0x%08x, size 0x%04x\n",