2016-01-04 22:25:00 +00:00
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References: bsc#956832 CVE-2015-8345
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2016-02-03 21:39:15 +00:00
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Subject: eepro100: Prevent two endless loops
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From: Stefan Weil sw@weilnetz.de Fri Nov 20 08:42:33 2015 +0100
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Date: Fri Nov 27 10:39:55 2015 +0800:
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Git: 00837731d254908a841d69298a4f9f077babaf24
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2016-01-04 22:25:00 +00:00
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2016-02-03 21:39:15 +00:00
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http://lists.nongnu.org/archive/html/qemu-devel/2015-11/msg04592.html
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shows an example how an endless loop in function action_command can
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be achieved.
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2016-01-04 22:25:00 +00:00
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2016-02-03 21:39:15 +00:00
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During my code review, I noticed a 2nd case which can result in an
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endless loop.
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2016-01-04 22:25:00 +00:00
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2016-02-03 21:39:15 +00:00
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Reported-by: Qinghao Tang <luodalongde@gmail.com>
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Signed-off-by: Stefan Weil <sw@weilnetz.de>
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Signed-off-by: Jason Wang <jasowang@redhat.com>
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2016-01-04 22:25:00 +00:00
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Index: xen-4.6.0-testing/tools/qemu-xen-dir-remote/hw/net/eepro100.c
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===================================================================
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--- xen-4.6.0-testing.orig/tools/qemu-xen-dir-remote/hw/net/eepro100.c
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+++ xen-4.6.0-testing/tools/qemu-xen-dir-remote/hw/net/eepro100.c
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2016-02-03 21:39:15 +00:00
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@@ -774,6 +774,11 @@ static void tx_command(EEPRO100State *s)
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#if 0
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uint16_t tx_buffer_el = lduw_le_pci_dma(&s->dev, tbd_address + 6);
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#endif
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+ if (tx_buffer_size == 0) {
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+ /* Prevent an endless loop. */
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+ logout("loop in %s:%u\n", __FILE__, __LINE__);
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2016-01-04 22:25:00 +00:00
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+ break;
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2016-02-03 21:39:15 +00:00
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+ }
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tbd_address += 8;
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TRACE(RXTX, logout
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("TBD (simplified mode): buffer address 0x%08x, size 0x%04x\n",
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@@ -855,6 +860,10 @@ static void set_multicast_list(EEPRO100S
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static void action_command(EEPRO100State *s)
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{
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+ /* The loop below won't stop if it gets special handcrafted data.
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+ Therefore we limit the number of iterations. */
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+ unsigned max_loop_count = 16;
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+
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for (;;) {
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bool bit_el;
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bool bit_s;
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@@ -870,6 +879,13 @@ static void action_command(EEPRO100State
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#if 0
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bool bit_sf = ((s->tx.command & COMMAND_SF) != 0);
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#endif
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+
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+ if (max_loop_count-- == 0) {
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+ /* Prevent an endless loop. */
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+ logout("loop in %s:%u\n", __FILE__, __LINE__);
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+ break;
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+ }
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+
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s->cu_offset = s->tx.link;
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TRACE(OTHER,
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logout("val=(cu start), status=0x%04x, command=0x%04x, link=0x%08x\n",
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