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#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2017 Oracle, Inc. All Rights Reserved.
#
# 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.
#
. ./common/preamble
_begin_fstest dangerous_fuzzers
PIDS=""
# Import common functions.
. ./common/filter
# real QA test starts here
_supported_fs xfs
_require_scratch_nocheck
_disable_dmesg_check
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
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