tests/generic/734

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2023 Oracle.  All Rights Reserved.
#
# FS QA Test No. 734
#
# This is a regression test for the kernel commit noted below.  The stale
# memory exposure can be exploited by creating a file with shared blocks,
# evicting the page cache for that file, and then funshareing at least one
# memory page's worth of data.  iomap will mark the page uptodate and dirty
# without ever reading the ondisk contents.
#
. ./common/preamble
_begin_fstest auto quick unshare clone

_cleanup()
{
	cd /
	rm -r -f $tmp.* $testdir
}


# Import common functions.
. ./common/filter
. ./common/reflink

_fixed_by_git_commit kernel 35d30c9cf127 \
	"iomap: don't skip reading in !uptodate folios when unsharing a range"

_require_test_reflink
_require_cp_reflink
_require_xfs_io_command "funshare"

testdir=$TEST_DIR/test-$seq
rm -rf $testdir
mkdir $testdir

# Create a file that is at least four pages in size and aligned to the
# file allocation unit size so that we don't trigger any unnecessary zeroing.
pagesz=$(_get_page_size)
alloc_unit=$(_get_file_block_size $TEST_DIR)
filesz=$(( ( (4 * pagesz) + alloc_unit - 1) / alloc_unit * alloc_unit))

echo "Create the original file and a clone"
_pwrite_byte 0x61 0 $filesz $testdir/file2.chk >> $seqres.full
_pwrite_byte 0x61 0 $filesz $testdir/file1 >> $seqres.full
_cp_reflink $testdir/file1 $testdir/file2
_cp_reflink $testdir/file1 $testdir/file3

_test_cycle_mount

cat $testdir/file3 > /dev/null

echo "Funshare at least one pagecache page"
$XFS_IO_PROG -c "funshare 0 $filesz" $testdir/file2
$XFS_IO_PROG -c "funshare 0 $filesz" $testdir/file3
_pwrite_byte 0x61 0 $filesz $testdir/file2.chk >> $seqres.full

echo "Check contents"

# file2 wasn't cached when it was unshared, but it should match
if ! cmp -s $testdir/file2.chk $testdir/file2; then
	echo "file2.chk does not match file2"

	echo "file2.chk contents" >> $seqres.full
	od -tx1 -Ad -c $testdir/file2.chk >> $seqres.full
	echo "file2 contents" >> $seqres.full
	od -tx1 -Ad -c $testdir/file2 >> $seqres.full
	echo "end bad contents" >> $seqres.full
fi

# file3 was cached when it was unshared, and it should match
if ! cmp -s $testdir/file2.chk $testdir/file3; then
	echo "file2.chk does not match file3"

	echo "file2.chk contents" >> $seqres.full
	od -tx1 -Ad -c $testdir/file2.chk >> $seqres.full
	echo "file3 contents" >> $seqres.full
	od -tx1 -Ad -c $testdir/file3 >> $seqres.full
	echo "end bad contents" >> $seqres.full
fi

# success, all done
status=0
exit