From: Petr Matousek <pmatouse@redhat.com>
Date: Wed, 17 Jun 2015 10:46:11 +0000 (+0200)
Subject: i8254: fix out-of-bounds memory access in pit_ioport_read()
X-Git-Tag: v2.4.0-rc0~43^2~9
X-Git-Url: http://git.qemu.org/?p=qemu.git;a=commitdiff_plain;h=d4862a87e31a51de9eb260f25c9e99a75efe3235;hp=9dacf32d2cbd66cbcce7944ebdfd6b2df20e33b8

i8254: fix out-of-bounds memory access in pit_ioport_read()

Due converting PIO to the new memory read/write api we no longer provide
separate I/O region lenghts for read and write operations. As a result,
reading from PIT Mode/Command register will end with accessing
pit->channels with invalid index.

Fix this by ignoring read from the Mode/Command register.

This is CVE-2015-3214.

Reported-by: Matt Tait <matttait@google.com>
Fixes: 0505bcdec8228d8de39ab1a02644e71999e7c052
Cc: qemu-stable@nongnu.org
Signed-off-by: Petr Matousek <pmatouse@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/hw/timer/i8254.c b/hw/timer/i8254.c
index 3450c98..9b65a33 100644
--- a/hw/timer/i8254.c
+++ b/hw/timer/i8254.c
@@ -196,6 +196,12 @@ static uint64_t pit_ioport_read(void *opaque, hwaddr addr,
     PITChannelState *s;
 
     addr &= 3;
+
+    if (addr == 3) {
+        /* Mode/Command register is write only, read is ignored */
+        return 0;
+    }
+
     s = &pit->channels[addr];
     if (s->status_latched) {
         s->status_latched = 0;