From 38b7ffbe3a1fa62f4d5177a3a572aa1c9abb1963 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Tue, 25 Mar 2014 14:23:33 +0100
Subject: [PATCH 26/49] qcow2: Fix backing file name length check

RH-Author: Kevin Wolf <kwolf@redhat.com>
Message-id: <1395753835-7591-27-git-send-email-kwolf@redhat.com>
Patchwork-id: n/a
O-Subject: [virt-devel] [EMBARGOED RHEL-7.0 qemu-kvm PATCH 26/48] qcow2: Fix backing file name length check
Bugzilla: 1066691
RH-Acked-by: Jeff Cody <jcody@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1066691
Upstream status: Series embargoed

len could become negative and would pass the check then. Nothing bad
happened because bdrv_pread() happens to return an error for negative
length values, but make variables for sizes unsigned anyway.

This patch also changes the behaviour to error out on invalid lengths
instead of silently truncating it to 1023.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2.c              |    9 ++++++---
 tests/qemu-iotests/080     |    8 ++++++++
 tests/qemu-iotests/080.out |    5 +++++
 3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index 8be82f0..a8ad9e1 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -445,7 +445,8 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
                       Error **errp)
 {
     BDRVQcowState *s = bs->opaque;
-    int len, i, ret = 0;
+    unsigned int len, i;
+    int ret = 0;
     QCowHeader header;
     QemuOpts *opts;
     Error *local_err = NULL;
@@ -720,8 +721,10 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags,
     /* read the backing file name */
     if (header.backing_file_offset != 0) {
         len = header.backing_file_size;
-        if (len > 1023) {
-            len = 1023;
+        if (len > MIN(1023, s->cluster_size - header.backing_file_offset)) {
+            error_setg(errp, "Backing file name too long");
+            ret = -EINVAL;
+            goto fail;
         }
         ret = bdrv_pread(bs->file, header.backing_file_offset,
                          bs->backing_file, len);
diff --git a/tests/qemu-iotests/080 b/tests/qemu-iotests/080
index 7255b6c..f3091a9 100755
--- a/tests/qemu-iotests/080
+++ b/tests/qemu-iotests/080
@@ -45,6 +45,7 @@ _supported_os Linux
 header_size=104
 
 offset_backing_file_offset=8
+offset_backing_file_size=16
 offset_l1_size=36
 offset_l1_table_offset=40
 offset_refcount_table_offset=48
@@ -135,6 +136,13 @@ poke_file "$TEST_IMG" "$offset_l1_table_offset" "\x12\x34\x56\x78\x90\xab\xcd\xe
 poke_file "$TEST_IMG" "$offset_l1_size" "\x00\x00\x00\x01"
 { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
 
+echo
+echo "== Invalid backing file size =="
+_make_test_img 64M
+poke_file "$TEST_IMG" "$offset_backing_file_offset" "\x00\x00\x00\x00\x00\x00\x10\x00"
+poke_file "$TEST_IMG" "$offset_backing_file_size" "\xff\xff\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
 # success, all done
 echo "*** done"
 rm -f $seq.full
diff --git a/tests/qemu-iotests/080.out b/tests/qemu-iotests/080.out
index 4ec2545..8103211 100644
--- a/tests/qemu-iotests/080.out
+++ b/tests/qemu-iotests/080.out
@@ -58,4 +58,9 @@ qemu-io: can't open device TEST_DIR/t.qcow2: Invalid L1 table offset
 no file open, try 'help open'
 qemu-io: can't open device TEST_DIR/t.qcow2: Invalid L1 table offset
 no file open, try 'help open'
+
+== Invalid backing file size ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
+qemu-io: can't open device TEST_DIR/t.qcow2: Backing file name too long
+no file open, try 'help open'
 *** done
-- 
1.7.1