#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2017 Oracle, Inc.  All Rights Reserved.
#
# FSQA Test No. ext4/040 (was shared/005)
#
# Since loff_t is a signed type, it is invalid for a filesystem to load
# an inode with i_size = -1ULL.  Unfortunately, nobody checks this,
# which means that we can trivially DoS the VFS by creating such a file
# and appending to it.  This causes an integer overflow in the routines
# underlying writeback, which results in the kernel locking up.
#
# So, create this malformed inode and try a buffered append to make
# sure we catch this situation.
#
. ./common/preamble
_begin_fstest dangerous_fuzzers

PIDS=""

# Import common functions.
. ./common/filter

# real QA test starts here
_supported_fs ext2 ext3 ext4
_require_scratch_nocheck
_disable_dmesg_check
_require_command "$DEBUGFS_PROG"

echo "Format and mount"
_scratch_mkfs  >> $seqres.full 2>&1
_scratch_mount

testdir=$SCRATCH_MNT
echo m > $testdir/a

echo "Corrupt filesystem"
_scratch_unmount
$DEBUGFS_PROG -w -R "sif /a size -1" $SCRATCH_DEV >> $seqres.full 2>&1

# check whether debugfs succeeds to set i_size to -1 or not
$DEBUGFS_PROG -R "stat /a" $SCRATCH_DEV 2>&1 | grep -q "Size: 18446744073709551615" || \
	_notrun "Could not set i_size to -1 successfully, skip test."

echo "Remount, try to append"
_scratch_mount
dd if=/dev/zero of=$testdir/a bs=512 count=1 oflag=append conv=notrunc >> $seqres.full 2>&1 || echo "Write did not succeed (ok)."
sync

# success, all done
status=0
exit