From 6d33e8e7dc9d40ea105feed4b39caa3e641569e8 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Wed, 26 Mar 2014 13:05:47 +0100
Subject: [PATCH] qcow2: Fix backing file name length check
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>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@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 36395289a9..cc1bfebf29 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;
@@ -721,8 +722,10 @@ 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 7255b6cca6..f3091a9377 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 4ec2545051..8103211064 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
--
2.30.2