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From 32dcdb3b1623e351d66bfe7cccbdcef3087f9b7b Mon Sep 17 00:00:00 2001
From: Max Reitz <mreitz@redhat.com>
Date: Mon, 13 Mar 2017 17:45:09 +0100
Subject: [PATCH 11/24] qcow2: Don't rely on free_cluster_index in
 alloc_refcount_block() (CVE-2014-0147)

RH-Author: Max Reitz <mreitz@redhat.com>
Message-id: <20170313174516.28044-3-mreitz@redhat.com>
Patchwork-id: 74274
O-Subject: [RHEL-7.4 qemu-kvm PATCH 2/9] qcow2: Don't rely on free_cluster_index in alloc_refcount_block() (CVE-2014-0147)
Bugzilla: 1427176
RH-Acked-by: Fam Zheng <famz@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

From: Kevin Wolf <kwolf@redhat.com>

free_cluster_index is only correct if update_refcount() was called from
an allocation function, and even there it's brittle because it's used to
protect unfinished allocations which still have a refcount of 0 - if it
moves in the wrong place, the unfinished allocation can be corrupted.

So not using it any more seems to be a good idea. Instead, use the
first requested cluster to do the calculations. Return -EAGAIN if
unfinished allocations could become invalid and let the caller restart
its search for some free clusters.

The context of creating a snapsnot is one situation where
update_refcount() is called outside of a cluster allocation. For this
case, the change fixes a buffer overflow if a cluster is referenced in
an L2 table that cannot be represented by an existing refcount block.
(new_table[refcount_table_index] was out of bounds)

[Bump the qemu-iotests 026 refblock_alloc.write leak count from 10 to
11.
--Stefan]

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit b106ad9185f35fc4ad669555ad0e79e276083bd7)

This patch was committed downstream before upstream (commit ID
a2b10eec76a72aa7fe63e797181b93f69de9600e), therefore the change to 026's
reference output is missing, which is amended by this backport.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 tests/qemu-iotests/026.out | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/qemu-iotests/026.out b/tests/qemu-iotests/026.out
index 0764389..5cedefc 100644
--- a/tests/qemu-iotests/026.out
+++ b/tests/qemu-iotests/026.out
@@ -491,7 +491,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 Event: refblock_alloc.write_blocks; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 
-10 leaked clusters were found on the image.
+11 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
@@ -515,7 +515,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 Event: refblock_alloc.write_table; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 
-10 leaked clusters were found on the image.
+11 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
@@ -539,7 +539,7 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 Event: refblock_alloc.switch_table; errno: 28; imm: off; once: off; write 
 write failed: No space left on device
 
-10 leaked clusters were found on the image.
+11 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 
-- 
1.8.3.1