#! /bin/bash
# FSQA Test No. 134
#
# 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 dio append to make sure we
# catch this situation.
#
#-----------------------------------------------------------------------
# Copyright (c) 2017 Oracle, Inc.  All Rights Reserved.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it would be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write the Free Software Foundation,
# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
#-----------------------------------------------------------------------

seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"

PIDS=""
tmp=/tmp/$$
status=1	# failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15

_cleanup()
{
	rm -f $tmp.*
}

# get standard environment, filters and checks
. ./common/rc
. ./common/filter

# real QA test starts here
_supported_os Linux
_supported_fs xfs
_require_scratch_nocheck
_disable_dmesg_check

rm -f $seqres.full

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

testdir=$SCRATCH_MNT
# make sure the write offset is 512-aligned
touch $testdir/a
inum=$(stat -c "%i" $testdir/a)

echo "Corrupt filesystem"
_scratch_unmount

# 1) Set the file size to the highest multiple of 512 below -1 so
#    that we can perform a dio write.
# 2) run two xfs_db commands to set core.size regardless of the special
#    argument "--" is needed or not.
_scratch_xfs_db -x -c "inode ${inum}" -c 'write core.size -- -512' >> $seqres.full 2>&1
_scratch_xfs_db -x -c "inode ${inum}" -c 'write core.size -512' >> $seqres.full 2>&1

# check core.size and _notrun if it's not set correctly
i_size=`_scratch_xfs_db -c "inode ${inum}" -c "print core.size" | $AWK_PROG '{print $3}'`
if [ $i_size -ne -512 ]; then
	_notrun "Could not set i_size to -512 successfully, skip test."
fi

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

# success, all done
status=0
exit