tests/ext4/055

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2021 Huawei.  All Rights Reserved.
#
# FS QA Test 055
#
# The preceding illegal memory access problem occurs due to tampering with the
# quota index information in the image.
#
# Regression test for kernel
# commit 9bf3d2033129 quota: check block number when reading the block in quota file
# commit d0e36a62bd4c quota: correct error number in free_dqentry()
#
# The test is based on a testcase from Zhang Yi <yi.zhang@huawei.com>.
#
. ./common/preamble
_begin_fstest auto quota

# real QA test starts here
_require_scratch_nocheck
_supported_fs ext4
_require_user fsgqa
_require_user fsgqa2
_require_command "$DEBUGFS_PROG" debugfs

echo "Silence is golden"

# The 1K blocksize is designed for debugfs.
_scratch_mkfs "-F -O quota -b 1024" > $seqres.full 2>&1

# Start from 0, fill block 1 with 6，replace the original 2.
# The purpose is change the normal index order from 1->2->3->4->5 to 1->6->0.
$DEBUGFS_PROG -w -R "zap_block -o 0 -l 1 -p 6 -f <3> 1" $SCRATCH_DEV >> $seqres.full 2>&1
_scratch_mount >> $seqres.full 2>&1

# Quota with user id 0 switch to quota with user id fsgqa, quota with user id 0 should
# be release, but it can not be released because of block 6 is used by other quota.
chown fsgqa:fsgqa $SCRATCH_MNT >> $seqres.full 2>&1
touch $SCRATCH_MNT/foo >> $seqres.full 2>&1

# In the process of deleting foo, will get the next block is 0 from block 6.
# Block 0 is illegitimate, because it is the superblock of quota file.
# It will take magic number from  block 0 as block number, and assign block number to
# info->dqi_free_blk
rm -f $SCRATCH_MNT/foo

# Switch the quota, the wrong block number will be larger then INX_MAX, and it will be
# return as a error code. Since the error code is not available, dqget() will change it
# to a invalid address, use this address will trigger problem.
chown fsgqa2:fsgqa2 $SCRATCH_MNT >> $seqres.full 2>&1

# success, all done
status=0
exit