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File CVE-2015-5154-qemut-check-array-bounds-before-writing-to-io_buffer.patch of Package xen (Revision b21b24cc28908c205bf774fc9be1b6af)

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From a9de14175548c04e0f8be7fae219246509ba46a9 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 3 Jun 2015 14:13:31 +0200
Subject: [PATCH 1/3] ide: Check array bounds before writing to io_buffer
 (CVE-2015-5154)

If the end_transfer_func of a command is called because enough data has
been read or written for the current PIO transfer, and it fails to
correctly call the command completion functions, the DRQ bit in the
status register and s->end_transfer_func may remain set. This allows the
guest to access further bytes in s->io_buffer beyond s->data_end, and
eventually overflowing the io_buffer.

One case where this currently happens is emulation of the ATAPI command
START STOP UNIT.

This patch fixes the problem by adding explicit array bounds checks
before accessing the buffer instead of relying on end_transfer_func to
function correctly.

Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 hw/ide/core.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

Index: xen-4.2.5-testing/tools/qemu-xen-traditional-dir-remote/hw/ide.c
===================================================================
--- xen-4.2.5-testing.orig/tools/qemu-xen-traditional-dir-remote/hw/ide.c
+++ xen-4.2.5-testing/tools/qemu-xen-traditional-dir-remote/hw/ide.c
@@ -3002,6 +3002,10 @@ static void ide_data_writew(void *opaque
     buffered_pio_write(s, addr, 2);
 
     p = s->data_ptr;
+    if (p + 2 > s->data_end) {
+        return;
+    }
+
     *(uint16_t *)p = le16_to_cpu(val);
     p += 2;
     s->data_ptr = p;
@@ -3021,6 +3025,10 @@ static uint32_t ide_data_readw(void *opa
     buffered_pio_read(s, addr, 2);
 
     p = s->data_ptr;
+    if (p + 2 > s->data_end) {
+        return 0;
+    }
+
     ret = cpu_to_le16(*(uint16_t *)p);
     p += 2;
     s->data_ptr = p;
@@ -3040,6 +3048,10 @@ static void ide_data_writel(void *opaque
     buffered_pio_write(s, addr, 4);
 
     p = s->data_ptr;
+    if (p + 4 > s->data_end) {
+        return;
+    }
+
     *(uint32_t *)p = le32_to_cpu(val);
     p += 4;
     s->data_ptr = p;
@@ -3059,6 +3071,10 @@ static uint32_t ide_data_readl(void *opa
     buffered_pio_read(s, addr, 4);
 
     p = s->data_ptr;
+    if (p + 4 > s->data_end) {
+        return 0;
+    }
+
     ret = cpu_to_le32(*(uint32_t *)p);
     p += 4;
     s->data_ptr = p;

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File CVE-2015-5154-qemut-check-array-bounds-before-writing-to-io_buffer.patch of Package xen (Revision b21b24cc28908c205bf774fc9be1b6af)

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