tests/generic/621

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright 2020 Google LLC
#
# FS QA Test No. 621
#
# Test for a race condition where a duplicate filename could be created in an
# encrypted directory while the directory's encryption key was being added
# concurrently.  This is a regression test for the following kernel commits:
#
#       968dd6d0c6d6 ("fscrypt: fix race allowing rename() and link() of ciphertext dentries")
#       75d18cd1868c ("ext4: prevent creating duplicate encrypted filenames")
#       bfc2b7e85189 ("f2fs: prevent creating duplicate encrypted filenames")
#       76786a0f0834 ("ubifs: prevent creating duplicate encrypted filenames")
#
# The first commit fixed the bug for the rename() and link() syscalls.
# The others fixed the bug for the other syscalls that create new filenames.
#
# Note, the bug wasn't actually reproducible on f2fs.
#
# The race condition worked as follows:
#    1. Initial state: an encrypted directory "dir" contains a file "foo",
#       but the directory's key hasn't been added yet so 'ls dir' shows an
#       encoded no-key name rather than "foo".
#    2. The key is added concurrently with mkdir("dir/foo") or another syscall
#       that creates a new filename and should fail if it already exists.
#        a. The syscall looks up "dir/foo", creating a negative no-key dentry
#           for "foo" since the directory's key hasn't been added yet.
#        b. The directory's key is added.
#        c. The syscall does the actual fs-level operation to create the
#           filename.  With the bug, the filesystem failed to detect that the
#           dentry was created without the key, potentially causing the
#           operation to unexpectedly succeed and add a duplicate filename.
#
# To test this, we try to reproduce the above race.  Afterwards we check for
# duplicate filenames, plus a few other things.
#
seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"

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

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

. ./common/rc
. ./common/filter
. ./common/encrypt
. ./common/renameat2

rm -f $seqres.full

_supported_fs generic
_require_scratch_encryption -v 2
_require_renameat2 noreplace

_scratch_mkfs_encrypted &>> $seqres.full
_scratch_mount

runtime=$((5 * TIME_FACTOR))
dir=$SCRATCH_MNT/dir

echo -e "\n# Creating encrypted directory containing files"
mkdir $dir
_add_enckey $SCRATCH_MNT "$TEST_RAW_KEY"
_set_encpolicy $dir $TEST_KEY_IDENTIFIER
for i in {1..100}; do
	touch $dir/$i
done

# This is the filename which we'll try to duplicate.
inode=$(stat -c %i $dir/100)

# ext4 checks for duplicate dentries when inserting one, which can hide the bug
# this test is testing for.  However, ext4 stops checking for duplicates once it
# finds space for the new dentry.  Therefore, we can circumvent ext4's duplicate
# checking by creating space at the beginning of the directory block.
rm $dir/1

echo -e "\n# Starting duplicate filename creator process"
(
	# Repeatedly try to create the filename $dir/100 (which already exists)
	# using syscalls that should fail if the file already exists: mkdir(),
	# mknod(), symlink(), link(), and renameat2(RENAME_NOREPLACE).  This
	# hopefully detects any one of them having the bug.  TODO: we should
	# also try open(O_EXCL|O_CREAT), but it needs a command-line tool.
	while [ ! -e $tmp.done ]; do
		if mkdir $dir/100 &> /dev/null; then
			touch $tmp.mkdir_succeeded
		fi
		if mknod $dir/100 c 5 5 &> /dev/null; then
			touch $tmp.mknod_succeeded
		fi
		if ln -s target $dir/100 &> /dev/null; then
			touch $tmp.symlink_succeeded
		fi
		if ln $dir/50 $dir/100 &> /dev/null; then
			touch $tmp.link_succeeded
		fi
		if $here/src/renameat2 -n $dir/50 $dir/100 &> /dev/null; then
			touch $tmp.rename_noreplace_succeeded
		fi
	done
) &

echo -e "\n# Starting add/remove enckey process"
(
	# Repeatedly add and remove the encryption key for $dir.  The actual
	# race this test is trying to reproduce occurs when adding the key.
	while [ ! -e $tmp.done ]; do
		_add_enckey $SCRATCH_MNT "$TEST_RAW_KEY" > /dev/null
		_rm_enckey $SCRATCH_MNT $TEST_KEY_IDENTIFIER > /dev/null
	done
) &

echo -e "\n# Running for a few seconds..."
sleep $runtime
echo -e "\n# Stopping subprocesses"
touch $tmp.done
wait

_add_enckey $SCRATCH_MNT "$TEST_RAW_KEY" > /dev/null

# Check for failure in several different ways, since different ways work on
# different filesystems.  E.g. ext4 shows duplicate filenames but ubifs doesn't.

echo -e "\n# Checking for duplicate filenames via readdir"
ls $dir | grep 100

echo -e "\n# Checking for unexpected change in inode number"
new_inode=$(stat -c %i $dir/100)
if [ $new_inode != $inode ]; then
	echo "Dentry changed inode number $inode => $new_inode!"
fi

echo -e "\n# Checking for operations that unexpectedly succeeded on an existing filename"
for op in "mkdir" "mknod" "symlink" "link" "rename_noreplace"; do
	if [ -e $tmp.${op}_succeeded ]; then
		echo "$op operation(s) on existing filename unexpectedly succeeded!"
	fi
done

# Also check that the fsck program can't find any duplicate filenames.
# For ext4, override _check_scratch_fs() so that we can specify -D (optimize
# directories); otherwise e2fsck doesn't check for duplicate filenames.
echo -e "\n# Checking for duplicate filenames via fsck"
_scratch_unmount
if [ "$FSTYP" = ext4 ]; then
	if ! e2fsck -f -y -D $SCRATCH_DEV &>> $seqres.full; then
		_log_err "filesystem on $SCRATCH_DEV is inconsistent"
	fi
else
	_check_scratch_fs
fi

# success, all done
status=0
exit