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#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2017 Oracle, Inc. All Rights Reserved.
#
# FSQA Test No. ext4/041 (was shared/007)
#
# 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 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
# Set the file size to the highest multiple of 512 below
# -1 so that we can perform a dio write.
$DEBUGFS_PROG -w -R "sif /a size 0xFFFFFFFFFFFFFE00" $SCRATCH_DEV >> $seqres.full 2>&1
# check whether debugfs succeeds to set i_size to -512 or not
$DEBUGFS_PROG -R "stat /a" $SCRATCH_DEV 2>&1 | grep -q "Size: 18446744073709551104" || \
_notrun "Could not set i_size to -512 successfully, skip test."
echo "Remount, try to append"
_scratch_mount
dd if=/dev/zero of=$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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