[PATCH v6 0/4] tests for btrfs fsverity

[PATCH v6 0/4] tests for btrfs fsverity

[Boris Burkov]

This patchset provides tests for fsverity support in btrfs.

It includes modifications for generic tests to pass with btrfs as well
as new tests.

--
v6:
- refactor "requires" for verity corruption tests so that other verity
  tests can run on btrfs even without the corruption command available.
  Also, explictly require xfs_io fiemap for all corruption tests.
- simplify and clarify "non-trivial EFBIG" calculation and documentation
  per suggestions by Eric Biggers.
- remove unnecessary adjustment to max file size in the new EFBIG test;
  the bug it worked around has been fixed.
v5:
- more idiomatic requires structure for making efbig test generic
- make efbig test use truncate instead of pwrite for making a big file
- improve documentation for efbig test approximation
- fix underscores vs dashes in btrfs_requires_corrupt_block
- improvements in missing/redundant requires invocations
- move orphan test image file to $TEST_DIR
- make orphan test replay/snapshot device size depend on log device
  instead of hard-coding it.
- rebase (signicant: no more "groups" file; use preamble)
v4:
- mark local variables
- get rid of redundant mounts and syncs
- use '_' in function names correctly
- add a test for the EFBIG case
- reduce usage of requires_btrfs_corrupt_block
- handle variable input when corrupting merkle tree
v3: rebase onto xfstests master branch
v2: pass generic tests, add logwrites test


Boris Burkov (4):
  btrfs: test btrfs specific fsverity corruption
  generic/574: corrupt btrfs merkle tree data
  btrfs: test verity orphans with dmlogwrites
  generic: test fs-verity EFBIG scenarios

 common/btrfs          |   5 ++
 common/config         |   1 +
 common/verity         |  43 +++++++++++
 tests/btrfs/290       | 166 ++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/290.out   |  25 +++++++
 tests/btrfs/291       | 161 ++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/291.out   |   2 +
 tests/generic/574     |   1 +
 tests/generic/690     |  66 +++++++++++++++++
 tests/generic/690.out |   7 ++
 10 files changed, 477 insertions(+)
 create mode 100755 tests/btrfs/290
 create mode 100644 tests/btrfs/290.out
 create mode 100755 tests/btrfs/291
 create mode 100644 tests/btrfs/291.out
 create mode 100755 tests/generic/690
 create mode 100644 tests/generic/690.out

-- 
2.34.0

[PATCH v6 1/4] btrfs: test btrfs specific fsverity corruption

[Boris Burkov]

There are some btrfs specific fsverity scenarios that don't map
neatly onto the tests in generic/574 like holes, inline extents,
and preallocated extents. Cover those in a btrfs specific test.

This test relies on the btrfs implementation of fsverity in the patch:
btrfs: initial fsverity support

and on btrfs-corrupt-block for corruption in the patches titled:
btrfs-progs: corrupt generic item data with btrfs-corrupt-block
btrfs-progs: expand corrupt_file_extent in btrfs-corrupt-block

Signed-off-by: Boris Burkov <boris@bur.io>
---
 common/btrfs        |   5 ++
 common/config       |   1 +
 common/verity       |  14 ++++
 tests/btrfs/290     | 166 ++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/290.out |  25 +++++++
 5 files changed, 211 insertions(+)
 create mode 100755 tests/btrfs/290
 create mode 100644 tests/btrfs/290.out

diff --git a/common/btrfs b/common/btrfs
index 5de926dd..6eb574be 100644
--- a/common/btrfs
+++ b/common/btrfs
@@ -496,3 +496,8 @@ _require_btrfs_support_sectorsize()
 	grep -wq $sectorsize /sys/fs/btrfs/features/supported_sectorsizes || \
 		_notrun "sectorsize $sectorsize is not supported"
 }
+
+_require_btrfs_corrupt_block()
+{
+	_require_command "$BTRFS_CORRUPT_BLOCK_PROG" btrfs-corrupt-block
+}
diff --git a/common/config b/common/config
index 0566ab4a..8cda36be 100644
--- a/common/config
+++ b/common/config
@@ -295,6 +295,7 @@ export BTRFS_UTIL_PROG=$(type -P btrfs)
 export BTRFS_SHOW_SUPER_PROG=$(type -P btrfs-show-super)
 export BTRFS_CONVERT_PROG=$(type -P btrfs-convert)
 export BTRFS_TUNE_PROG=$(type -P btrfstune)
+export BTRFS_CORRUPT_BLOCK_PROG=$(type -P btrfs-corrupt-block)
 export XFS_FSR_PROG=$(type -P xfs_fsr)
 export MKFS_NFS_PROG="false"
 export MKFS_CIFS_PROG="false"
diff --git a/common/verity b/common/verity
index 38eea157..eec8ae72 100644
--- a/common/verity
+++ b/common/verity
@@ -3,6 +3,8 @@
 #
 # Functions for setting up and testing fs-verity
 
+. common/btrfs
+
 _require_scratch_verity()
 {
 	_require_scratch
@@ -48,6 +50,15 @@ _require_scratch_verity()
 	FSV_BLOCK_SIZE=$(get_page_size)
 }
 
+# Check for userspace tools needed to corrupt verity data or metadata.
+_require_fsverity_corruption()
+{
+	_require_xfs_io_command "fiemap"
+	if [ $FSTYP == "btrfs" ]; then
+		_require_btrfs_corrupt_block
+	fi
+}
+
 # Check for CONFIG_FS_VERITY_BUILTIN_SIGNATURES=y, as well as the userspace
 # commands needed to generate certificates and add them to the kernel.
 _require_fsverity_builtin_signatures()
@@ -147,6 +158,9 @@ _scratch_mkfs_verity()
 	ext4|f2fs)
 		_scratch_mkfs -O verity
 		;;
+	btrfs)
+		_scratch_mkfs
+		;;
 	*)
 		_notrun "No verity support for $FSTYP"
 		;;
diff --git a/tests/btrfs/290 b/tests/btrfs/290
new file mode 100755
index 00000000..0276527d
--- /dev/null
+++ b/tests/btrfs/290
@@ -0,0 +1,166 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2021 Facebook, Inc. All Rights Reserved.
+#
+# FS QA Test 290
+#
+# Test btrfs support for fsverity.
+# This test extends the generic fsverity testing by corrupting inline extents,
+# preallocated extents, holes, and the Merkle descriptor in a btrfs-aware way.
+#
+. ./common/preamble
+_begin_fstest auto quick verity
+
+# Import common functions.
+. ./common/filter
+. ./common/verity
+
+# real QA test starts here
+_supported_fs btrfs
+_require_scratch_verity
+_require_scratch_nocheck
+_require_odirect
+_require_xfs_io_command "falloc"
+_require_fsverity_corruption
+
+get_ino() {
+	local file=$1
+	stat -c "%i" $file
+}
+
+validate() {
+	local f=$1
+	local sz=$(_get_filesize $f)
+	# buffered io
+	echo $(basename $f)
+	$XFS_IO_PROG -rc "pread -q 0 $sz" $f 2>&1 | _filter_scratch
+	# direct io
+	$XFS_IO_PROG -rdc "pread -q 0 $sz" $f 2>&1 | _filter_scratch
+}
+
+# corrupt the data portion of an inline extent
+corrupt_inline() {
+	local f=$SCRATCH_MNT/inl
+	$XFS_IO_PROG -fc "pwrite -q -S 0x58 0 42" $f
+	local ino=$(get_ino $f)
+	_fsv_enable $f
+	_scratch_unmount
+	# inline data starts at disk_bytenr
+	# overwrite the first u64 with random bogus junk
+	$BTRFS_CORRUPT_BLOCK_PROG -i $ino -x 0 -f disk_bytenr $SCRATCH_DEV > /dev/null 2>&1
+	_scratch_mount
+	validate $f
+}
+
+# preallocate a file, then corrupt it by changing it to a regular file
+corrupt_prealloc_to_reg() {
+	local f=$SCRATCH_MNT/prealloc
+	$XFS_IO_PROG -fc "falloc 0 12k" $f
+	local ino=$(get_ino $f)
+	_fsv_enable $f
+	_scratch_unmount
+	# set extent type from prealloc (2) to reg (1)
+	$BTRFS_CORRUPT_BLOCK_PROG -i $ino -x 0 -f type -v 1 $SCRATCH_DEV >/dev/null 2>&1
+	_scratch_mount
+	validate $f
+}
+
+# corrupt a regular file by changing the type to preallocated
+corrupt_reg_to_prealloc() {
+	local f=$SCRATCH_MNT/reg
+	$XFS_IO_PROG -fc "pwrite -q -S 0x58 0 12288" $f
+	local ino=$(get_ino $f)
+	_fsv_enable $f
+	_scratch_unmount
+	# set type from reg (1) to prealloc (2)
+	$BTRFS_CORRUPT_BLOCK_PROG -i $ino -x 0 -f type -v 2 $SCRATCH_DEV >/dev/null 2>&1
+	_scratch_mount
+	validate $f
+}
+
+# corrupt a file by punching a hole
+corrupt_punch_hole() {
+	local f=$SCRATCH_MNT/punch
+	$XFS_IO_PROG -fc "pwrite -q -S 0x58 0 12288" $f
+	local ino=$(get_ino $f)
+	# make a new extent in the middle, sync so the writes don't coalesce
+	$XFS_IO_PROG -c sync $SCRATCH_MNT
+	$XFS_IO_PROG -fc "pwrite -q -S 0x59 4096 4096" $f
+	_fsv_enable $f
+	_scratch_unmount
+	# change disk_bytenr to 0, representing a hole
+	$BTRFS_CORRUPT_BLOCK_PROG -i $ino -x 4096 -f disk_bytenr -v 0 $SCRATCH_DEV > /dev/null 2>&1
+	_scratch_mount
+	validate $f
+}
+
+# plug hole
+corrupt_plug_hole() {
+	local f=$SCRATCH_MNT/plug
+	$XFS_IO_PROG -fc "pwrite -q -S 0x58 0 12288" $f
+	local ino=$(get_ino $f)
+	$XFS_IO_PROG -fc "falloc 4k 4k" $f
+	_fsv_enable $f
+	_scratch_unmount
+	# change disk_bytenr to some value, plugging the hole
+	$BTRFS_CORRUPT_BLOCK_PROG -i $ino -x 4096 -f disk_bytenr -v 13639680 $SCRATCH_DEV > /dev/null 2>&1
+	_scratch_mount
+	validate $f
+}
+
+# corrupt the fsverity descriptor item indiscriminately (causes EINVAL)
+corrupt_verity_descriptor() {
+	local f=$SCRATCH_MNT/desc
+	$XFS_IO_PROG -fc "pwrite -q -S 0x58 0 12288" $f
+	local ino=$(get_ino $f)
+	_fsv_enable $f
+	_scratch_unmount
+	# key for the descriptor item is <inode, BTRFS_VERITY_DESC_ITEM_KEY, 1>,
+	# 88 is X. So we write 5 Xs to the start of the descriptor
+	$BTRFS_CORRUPT_BLOCK_PROG -r 5 -I $ino,36,1 -v 88 -o 0 -b 5 $SCRATCH_DEV > /dev/null 2>&1
+	_scratch_mount
+	validate $f
+}
+
+# specifically target the root hash in the descriptor (causes EIO)
+corrupt_root_hash() {
+	local f=$SCRATCH_MNT/roothash
+	$XFS_IO_PROG -fc "pwrite -q -S 0x58 0 12288" $f
+	local ino=$(get_ino $f)
+	_fsv_enable $f
+	_scratch_unmount
+	$BTRFS_CORRUPT_BLOCK_PROG -r 5 -I $ino,36,1 -v 88 -o 16 -b 1 $SCRATCH_DEV > /dev/null 2>&1
+	_scratch_mount
+	validate $f
+}
+
+# corrupt the Merkle tree data itself
+corrupt_merkle_tree() {
+	local f=$SCRATCH_MNT/merkle
+	$XFS_IO_PROG -fc "pwrite -q -S 0x58 0 12288" $f
+	local ino=$(get_ino $f)
+	_fsv_enable $f
+	_scratch_unmount
+	# key for the descriptor item is <inode, BTRFS_VERITY_MERKLE_ITEM_KEY, 0>,
+	# 88 is X. So we write 5 Xs to somewhere in the middle of the first
+	# merkle item
+	$BTRFS_CORRUPT_BLOCK_PROG -r 5 -I $ino,37,0 -v 88 -o 100 -b 5 $SCRATCH_DEV > /dev/null 2>&1
+	_scratch_mount
+	validate $f
+}
+
+# real QA test starts here
+_scratch_mkfs >/dev/null
+_scratch_mount
+
+corrupt_inline
+corrupt_prealloc_to_reg
+corrupt_reg_to_prealloc
+corrupt_punch_hole
+corrupt_plug_hole
+corrupt_verity_descriptor
+corrupt_root_hash
+corrupt_merkle_tree
+
+status=0
+exit
diff --git a/tests/btrfs/290.out b/tests/btrfs/290.out
new file mode 100644
index 00000000..056b114b
--- /dev/null
+++ b/tests/btrfs/290.out
@@ -0,0 +1,25 @@
+QA output created by 290
+inl
+pread: Input/output error
+pread: Input/output error
+prealloc
+pread: Input/output error
+pread: Input/output error
+reg
+pread: Input/output error
+pread: Input/output error
+punch
+pread: Input/output error
+pread: Input/output error
+plug
+pread: Input/output error
+pread: Input/output error
+desc
+SCRATCH_MNT/desc: Invalid argument
+SCRATCH_MNT/desc: Invalid argument
+roothash
+pread: Input/output error
+pread: Input/output error
+merkle
+pread: Input/output error
+pread: Input/output error
-- 
2.34.0

[PATCH v6 2/4] generic/574: corrupt btrfs merkle tree data

[Boris Burkov]

generic/574 has tests for corrupting the merkle tree data stored by the
filesystem. Since btrfs uses a different scheme for storing this data,
the existing logic for corrupting it doesn't work out of the box. Adapt
it to properly corrupt btrfs merkle items.

This test relies on the btrfs implementation of fsverity in the patch:
btrfs: initial fsverity support

and on btrfs-corrupt-block for corruption in the patches titled:
btrfs-progs: corrupt generic item data with btrfs-corrupt-block
btrfs-progs: expand corrupt_file_extent in btrfs-corrupt-block

Signed-off-by: Boris Burkov <boris@bur.io>
---
 common/verity     | 18 ++++++++++++++++++
 tests/generic/574 |  1 +
 2 files changed, 19 insertions(+)

diff --git a/common/verity b/common/verity
index eec8ae72..07d9d3fe 100644
--- a/common/verity
+++ b/common/verity
@@ -322,6 +322,24 @@ _fsv_scratch_corrupt_merkle_tree()
 		(( offset += ($(_get_filesize $file) + 65535) & ~65535 ))
 		_fsv_scratch_corrupt_bytes $file $offset
 		;;
+	btrfs)
+		local ino=$(stat -c '%i' $file)
+		_scratch_unmount
+		local byte=""
+		while read -n 1 byte; do
+			if [ -z $byte ]; then
+				break
+			fi
+			local ascii=$(printf "%d" "'$byte'")
+			# This command will find a Merkle tree item for the inode (-I $ino,37,0)
+			# in the default filesystem tree (-r 5) and corrupt one byte (-b 1) at
+			# $offset (-o $offset) with the ascii representation of the byte we read
+			# (-v $ascii)
+			$BTRFS_CORRUPT_BLOCK_PROG -r 5 -I $ino,37,0 -v $ascii -o $offset -b 1 $SCRATCH_DEV
+			(( offset += 1 ))
+		done
+		_scratch_mount
+		;;
 	*)
 		_fail "_fsv_scratch_corrupt_merkle_tree() unimplemented on $FSTYP"
 		;;
diff --git a/tests/generic/574 b/tests/generic/574
index 882baa21..6cb7eff6 100755
--- a/tests/generic/574
+++ b/tests/generic/574
@@ -27,6 +27,7 @@ _cleanup()
 # real QA test starts here
 _supported_fs generic
 _require_scratch_verity
+_require_fsverity_corruption
 _disable_fsverity_signatures
 
 _scratch_mkfs_verity &>> $seqres.full
-- 
2.34.0

[PATCH v6 3/4] btrfs: test verity orphans with dmlogwrites

[Boris Burkov]

The behavior of orphans is most interesting across mounts, interrupted
at arbitrary points during fsverity enable. To cover as many such cases
as possible, use dmlogwrites and dmsnapshot as in
log-writes/replay-individual.sh. At each log entry, we want to assert a
somewhat complicated invariant:

If verity has not yet started: an orphan indicates that verity has
started.
If verity has started: mount should handle the orphan and blow away
verity data: expect 0 merkle items after mounting the snapshot dev. If
we can measure the file, verity has finished.
If verity has finished: the orphan should be gone, so mount should not
blow away merkle items. Expect the same number of merkle items before
and after mounting the snapshot dev.

Note that this relies on grepping btrfs inspect-internal dump-tree.
Until btrfs-progs has the ability to print the new Merkle items, they
will show up as UNKNOWN.36/37.

Signed-off-by: Boris Burkov <boris@bur.io>
---
 tests/btrfs/291     | 161 ++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/291.out |   2 +
 2 files changed, 163 insertions(+)
 create mode 100755 tests/btrfs/291
 create mode 100644 tests/btrfs/291.out

diff --git a/tests/btrfs/291 b/tests/btrfs/291
new file mode 100755
index 00000000..1bb3f1b3
--- /dev/null
+++ b/tests/btrfs/291
@@ -0,0 +1,161 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2021 Facebook, Inc. All Rights Reserved.
+#
+# FS QA Test 291
+#
+# Test btrfs consistency after each FUA while enabling verity on a file
+# This test works by following the pattern in log-writes/replay-individual.sh:
+# 1. run a workload (verity + sync) while logging to the log device
+# 2. replay an entry to the replay device
+# 3. snapshot the replay device to the snapshot device
+# 4. run destructive tests on the snapshot device (e.g. mount with orphans)
+# 5. goto 2
+#
+. ./common/preamble
+_begin_fstest auto verity
+
+# Override the default cleanup function.
+_cleanup()
+{
+	cd /
+	_log_writes_cleanup &> /dev/null
+	rm -f $img
+	$LVM_PROG vgremove -f -y $vgname >>$seqres.full 2>&1
+	losetup -d $loop_dev >>$seqres.full 2>&1
+}
+
+# Import common functions.
+. ./common/filter
+. ./common/attr
+. ./common/dmlogwrites
+. ./common/verity
+
+# real QA test starts here
+_supported_fs btrfs
+
+_require_scratch
+_require_test
+_require_log_writes
+_require_dm_target snapshot
+_require_command $LVM_PROG lvm
+_require_scratch_verity
+_require_btrfs_command inspect-internal dump-tree
+_require_test_program "log-writes/replay-log"
+
+sync_loop() {
+	i=$1
+	[ -z "$i" ] && _fail "sync loop needs a number of iterations"
+	while [ $i -gt 0 ]
+	do
+		$XFS_IO_PROG -c sync $SCRATCH_MNT
+		let i-=1
+	done
+}
+
+dump_tree() {
+	local dev=$1
+	$BTRFS_UTIL_PROG inspect-internal dump-tree $dev
+}
+
+count_item() {
+	local dev=$1
+	local item=$2
+	dump_tree $dev | grep -c $item
+}
+
+_log_writes_init $SCRATCH_DEV
+_log_writes_mkfs
+_log_writes_mount
+
+f=$SCRATCH_MNT/fsv
+MB=$((1024 * 1024))
+img=$TEST_DIR/$$.img
+$XFS_IO_PROG -fc "pwrite -q 0 $((10 * $MB))" $f
+$XFS_IO_PROG -c sync $SCRATCH_MNT
+sync_loop 10 &
+sync_proc=$!
+_fsv_enable $f
+$XFS_IO_PROG -c sync $SCRATCH_MNT
+wait $sync_proc
+
+_log_writes_unmount
+_log_writes_remove
+
+# the snapshot and the replay will each be the size of the log writes dev
+# so we create a loop device of size 2 * logwrites and then split it into
+# replay and snapshot with lvm.
+log_writes_blocks=$(blockdev --getsz $LOGWRITES_DEV)
+replay_bytes=$((512 * $log_writes_blocks))
+img_bytes=$((2 * $replay_bytes))
+
+$XFS_IO_PROG -fc "pwrite -q -S 0 $img_bytes $MB" $img >>$seqres.full 2>&1 || \
+	_fail "failed to create image for loop device"
+loop_dev=$(losetup -f --show $img)
+vgname=vg_replay
+lvname=lv_replay
+replay_dev=/dev/mapper/vg_replay-lv_replay
+snapname=lv_snap
+snap_dev=/dev/mapper/vg_replay-$snapname
+
+$LVM_PROG vgcreate -f $vgname $loop_dev >>$seqres.full 2>&1 || _fail "failed to vgcreate $vgname"
+$LVM_PROG lvcreate -L "$replay_bytes"B -n $lvname $vgname -y >>$seqres.full 2>&1 || \
+	_fail "failed to lvcreate $lvname"
+$UDEV_SETTLE_PROG >>$seqres.full 2>&1
+
+replay_log_prog=$here/src/log-writes/replay-log
+num_entries=$($replay_log_prog --log $LOGWRITES_DEV --num-entries)
+entry=$($replay_log_prog --log $LOGWRITES_DEV --replay $replay_dev --find --end-mark mkfs | cut -d@ -f1)
+$replay_log_prog --log $LOGWRITES_DEV --replay $replay_dev --limit $entry || \
+	_fail "failed to replay to start entry $entry"
+let entry+=1
+
+# state = 0: verity hasn't started
+# state = 1: verity underway
+# state = 2: verity done
+state=0
+while [ $entry -lt $num_entries ];
+do
+	$replay_log_prog --limit 1 --log $LOGWRITES_DEV --replay $replay_dev --start $entry || \
+		_fail "failed to take replay step at entry: $entry"
+
+	$LVM_PROG lvcreate -s -L 4M -n $snapname $vgname/$lvname >>$seqres.full 2>&1 || \
+		_fail "Failed to create snapshot"
+	$UDEV_SETTLE_PROG >>$seqres.full 2>&1
+
+	orphan=$(count_item $snap_dev ORPHAN)
+	if [ $state -eq 0 ]; then
+		[ $orphan -gt 0 ] && state=1
+	fi
+
+	pre_mount=$(count_item $snap_dev UNKNOWN.3[67])
+	_mount $snap_dev $SCRATCH_MNT || _fail "mount failed at entry $entry"
+	fsverity measure $SCRATCH_MNT/fsv >>$seqres.full 2>&1
+	measured=$?
+	umount $SCRATCH_MNT
+	[ $state -eq 1 ] && [ $measured -eq 0 ] && state=2
+	[ $state -eq 2 ] && ([ $measured -eq 0 ] || _fail "verity done, but measurement failed at entry $entry")
+	post_mount=$(count_item $snap_dev UNKNOWN.3[67])
+
+	echo "entry: $entry, state: $state, orphan: $orphan, pre_mount: $pre_mount, post_mount: $post_mount" >> $seqres.full
+
+	if [ $state -eq 1 ]; then
+		[ $post_mount -eq 0 ] || \
+			_fail "mount failed to clear under-construction merkle items pre: $pre_mount, post: $post_mount at entry $entry";
+	fi
+	if [ $state -eq 2 ]; then
+		[ $pre_mount -gt 0 ] || \
+			_fail "expected to have verity items before mount at entry $entry"
+		[ $pre_mount -eq $post_mount ] || \
+			_fail "mount cleared merkle items after verity was enabled $pre_mount vs $post_mount at entry $entry";
+	fi
+
+	let entry+=1
+	$LVM_PROG lvremove $vgname/$snapname -y >>$seqres.full
+done
+
+echo "Silence is golden"
+
+# success, all done
+status=0
+exit
diff --git a/tests/btrfs/291.out b/tests/btrfs/291.out
new file mode 100644
index 00000000..04605c70
--- /dev/null
+++ b/tests/btrfs/291.out
@@ -0,0 +1,2 @@
+QA output created by 291
+Silence is golden
-- 
2.34.0

[PATCH v6 4/4] generic: test fs-verity EFBIG scenarios

[Boris Burkov]

btrfs, ext4, and f2fs cache the Merkle tree past EOF, which restricts
the maximum file size beneath the normal maximum. Test the logic in
those filesystems against files with sizes near the maximum.

To work properly, this does require some understanding of the practical
but not standardized layout of the Merkle tree. This is a bit unpleasant
and could make the test incorrect in the future, if the implementation
changes. On the other hand, it feels quite useful to test this tricky
edge case. It could perhaps be made more generic by adding some ioctls
to let the file system communicate the maximum file size for a verity
file or some information about the storage of the Merkle tree.

Signed-off-by: Boris Burkov <boris@bur.io>
---
 common/verity         | 11 ++++++++
 tests/generic/690     | 66 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/690.out |  7 +++++
 3 files changed, 84 insertions(+)
 create mode 100755 tests/generic/690
 create mode 100644 tests/generic/690.out

diff --git a/common/verity b/common/verity
index 07d9d3fe..8be86ef7 100644
--- a/common/verity
+++ b/common/verity
@@ -345,3 +345,14 @@ _fsv_scratch_corrupt_merkle_tree()
 		;;
 	esac
 }
+
+_require_fsverity_max_file_size_limit()
+{
+	case $FSTYP in
+	btrfs|ext4|f2fs)
+		;;
+	*)
+		_notrun "$FSTYP does not store verity data past EOF; no special file size limit"
+		;;
+	esac
+}
diff --git a/tests/generic/690 b/tests/generic/690
new file mode 100755
index 00000000..77906dd8
--- /dev/null
+++ b/tests/generic/690
@@ -0,0 +1,66 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2021 Facebook, Inc.  All Rights Reserved.
+#
+# FS QA Test 690
+#
+# fs-verity requires the filesystem to decide how it stores the Merkle tree,
+# which can be quite large.
+# It is convenient to treat the Merkle tree as past EOF, and ext4, f2fs, and
+# btrfs do so in at least some fashion. This leads to an edge case where a
+# large file can be under the file system file size limit, but trigger EFBIG
+# on enabling fs-verity. Test enabling verity on some large files to exercise
+# EFBIG logic for filesystems with fs-verity specific limits.
+#
+. ./common/preamble
+_begin_fstest auto quick verity
+
+
+# Import common functions.
+. ./common/filter
+. ./common/verity
+
+# real QA test starts here
+_supported_fs generic
+_require_test
+_require_math
+_require_scratch_verity
+_require_fsverity_max_file_size_limit
+_require_scratch_nocheck
+
+_scratch_mkfs_verity &>> $seqres.full
+_scratch_mount
+
+fsv_file=$SCRATCH_MNT/file.fsv
+
+max_sz=$(_get_max_file_size)
+_fsv_scratch_begin_subtest "way too big: fail on first merkle block"
+# have to go back by 4096 from max to not hit the fsverity MAX_LEVELS check.
+truncate -s $max_sz $fsv_file
+_fsv_enable $fsv_file |& _filter_scratch
+
+# The goal of this second test is to make a big enough file that we trip the
+# EFBIG codepath, but not so big that we hit it immediately when writing the
+# first Merkle leaf.
+#
+# The Merkle tree is stored with the leaf node level (L0) last, but it is
+# written first.  To get an interesting overflow, we need the maximum file size
+# (MAX) to be in the middle of L0 -- ideally near the beginning of L0 so that we
+# don't have to write many blocks before getting an error.
+#
+# With SHA-256 and 4K blocks, there are 128 hashes per block.  Thus, ignoring
+# padding, L0 is 1/128 of the file size while the other levels in total are
+# 1/128**2 + 1/128**3 + 1/128**4 + ... = 1/16256 of the file size.  So still
+# ignoring padding, for L0 start exactly at MAX, the file size must be s such
+# that s + s/16256 = MAX, i.e. s = MAX * (16256/16257).  Then to get a file size
+# where MAX occurs *near* the start of L0 rather than *at* the start, we can
+# just subtract an overestimate of the padding: 64K after the file contents,
+# then 4K per level, where the consideration of 8 levels is sufficient.
+sz=$(echo "scale=20; $max_sz * (16256/16257) - 65536 - 4096*8" | $BC -q | cut -d. -f1)
+_fsv_scratch_begin_subtest "still too big: fail on first invalid merkle block"
+truncate -s $sz $fsv_file
+_fsv_enable $fsv_file |& _filter_scratch
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/690.out b/tests/generic/690.out
new file mode 100644
index 00000000..a3e2b9b9
--- /dev/null
+++ b/tests/generic/690.out
@@ -0,0 +1,7 @@
+QA output created by 690
+
+# way too big: fail on first merkle block
+ERROR: FS_IOC_ENABLE_VERITY failed on 'SCRATCH_MNT/file.fsv': File too large
+
+# still too big: fail on first invalid merkle block
+ERROR: FS_IOC_ENABLE_VERITY failed on 'SCRATCH_MNT/file.fsv': File too large
-- 
2.34.0

Re: [PATCH v6 1/4] btrfs: test btrfs specific fsverity corruption

[Eric Biggers]

On Mon, Feb 14, 2022 at 04:09:55PM -0800, Boris Burkov wrote:
> diff --git a/common/verity b/common/verity
> index 38eea157..eec8ae72 100644
> --- a/common/verity
> +++ b/common/verity
> @@ -3,6 +3,8 @@
>  #
>  # Functions for setting up and testing fs-verity
>  
> +. common/btrfs

Why does common/btrfs need to be included here?

> +# Check for userspace tools needed to corrupt verity data or metadata.
> +_require_fsverity_corruption()
> +{
> +	_require_xfs_io_command "fiemap"
> +	if [ $FSTYP == "btrfs" ]; then
> +		_require_btrfs_corrupt_block
> +	fi
> +}

Which function(s), specifically, is this function a prerequisite for?  Based on
the name, it sounds like it would be a prerequisite for calling
_fsv_scratch_corrupt_bytes() and _fsv_scratch_corrupt_merkle_tree().  But that's
apparently not the case, seeing as generic/576 calls
_fsv_scratch_corrupt_bytes() but doesn't call _require_fsverity_corruption(),
and your new test btrfs/290 calls _require_fsverity_corruption() but doesn't
call either _fsv_scratch_corrupt_bytes() or _fsv_scratch_corrupt_merkle_tree().

So, the purpose of this function is unclear.

Perhaps it should be a prerequisite for all _fsv_scratch_corrupt*() functions,
and btrfs/290 should check for btrfs-corrupt-block directly?

- Eric

Re: [PATCH v6 2/4] generic/574: corrupt btrfs merkle tree data

[Eric Biggers]

On Mon, Feb 14, 2022 at 04:09:56PM -0800, Boris Burkov wrote:
> generic/574 has tests for corrupting the merkle tree data stored by the
> filesystem. Since btrfs uses a different scheme for storing this data,
> the existing logic for corrupting it doesn't work out of the box. Adapt
> it to properly corrupt btrfs merkle items.
> 
> This test relies on the btrfs implementation of fsverity in the patch:
> btrfs: initial fsverity support
> 
> and on btrfs-corrupt-block for corruption in the patches titled:
> btrfs-progs: corrupt generic item data with btrfs-corrupt-block
> btrfs-progs: expand corrupt_file_extent in btrfs-corrupt-block
> 
> Signed-off-by: Boris Burkov <boris@bur.io>
> ---
>  common/verity     | 18 ++++++++++++++++++
>  tests/generic/574 |  1 +
>  2 files changed, 19 insertions(+)
> 
> diff --git a/common/verity b/common/verity
> index eec8ae72..07d9d3fe 100644
> --- a/common/verity
> +++ b/common/verity
> @@ -322,6 +322,24 @@ _fsv_scratch_corrupt_merkle_tree()
>  		(( offset += ($(_get_filesize $file) + 65535) & ~65535 ))
>  		_fsv_scratch_corrupt_bytes $file $offset
>  		;;
> +	btrfs)
> +		local ino=$(stat -c '%i' $file)
> +		_scratch_unmount
> +		local byte=""
> +		while read -n 1 byte; do
> +			if [ -z $byte ]; then
> +				break
> +			fi

'[ -z $byte ]' could use quotes around $byte.  But isn't that check unneeded at
all, given that 'read' will fail when EOF is reached?

- Eric

Re: [PATCH v6 4/4] generic: test fs-verity EFBIG scenarios

[Eric Biggers]

On Mon, Feb 14, 2022 at 04:09:58PM -0800, Boris Burkov wrote:
> diff --git a/tests/generic/690 b/tests/generic/690
> new file mode 100755
> index 00000000..77906dd8
> --- /dev/null
> +++ b/tests/generic/690
> @@ -0,0 +1,66 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2021 Facebook, Inc.  All Rights Reserved.
> +#
> +# FS QA Test 690
> +#
> +# fs-verity requires the filesystem to decide how it stores the Merkle tree,
> +# which can be quite large.
> +# It is convenient to treat the Merkle tree as past EOF, and ext4, f2fs, and
> +# btrfs do so in at least some fashion. This leads to an edge case where a
> +# large file can be under the file system file size limit, but trigger EFBIG
> +# on enabling fs-verity. Test enabling verity on some large files to exercise
> +# EFBIG logic for filesystems with fs-verity specific limits.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick verity
> +
> +
> +# Import common functions.
> +. ./common/filter
> +. ./common/verity
> +
> +# real QA test starts here
> +_supported_fs generic
> +_require_test
> +_require_math
> +_require_scratch_verity
> +_require_fsverity_max_file_size_limit
> +_require_scratch_nocheck

Why is _require_scratch_nocheck() needed?  _require_scratch_verity() already
does _require_scratch(), and I don't see why skipping fsck would be needed.

> +# have to go back by 4096 from max to not hit the fsverity MAX_LEVELS check.
> +truncate -s $max_sz $fsv_file

The above comment should be removed.

- Eric

Re: [PATCH v6 1/4] btrfs: test btrfs specific fsverity corruption

[Boris Burkov]

On Mon, Mar 14, 2022 at 11:58:35PM +0000, Eric Biggers wrote:
> On Mon, Feb 14, 2022 at 04:09:55PM -0800, Boris Burkov wrote:
> > diff --git a/common/verity b/common/verity
> > index 38eea157..eec8ae72 100644
> > --- a/common/verity
> > +++ b/common/verity
> > @@ -3,6 +3,8 @@
> >  #
> >  # Functions for setting up and testing fs-verity
> >  
> > +. common/btrfs
> 
> Why does common/btrfs need to be included here?

To get _require_btrfs_corrupt_block. I can move that in here, as it
doesn't have any non-verity use case in btrfs tests yet. But it should
probably stay a named function rather than get rolled into
require_fsverity_corruption if I make btrfs/290 use it directly (which I
think is a good suggestion).

> 
> > +# Check for userspace tools needed to corrupt verity data or metadata.
> > +_require_fsverity_corruption()
> > +{
> > +	_require_xfs_io_command "fiemap"
> > +	if [ $FSTYP == "btrfs" ]; then
> > +		_require_btrfs_corrupt_block
> > +	fi
> > +}
> 
> Which function(s), specifically, is this function a prerequisite for?  Based on
> the name, it sounds like it would be a prerequisite for calling
> _fsv_scratch_corrupt_bytes() and _fsv_scratch_corrupt_merkle_tree().  But that's
> apparently not the case, seeing as generic/576 calls
> _fsv_scratch_corrupt_bytes() but doesn't call _require_fsverity_corruption(),
> and your new test btrfs/290 calls _require_fsverity_corruption() but doesn't
> call either _fsv_scratch_corrupt_bytes() or _fsv_scratch_corrupt_merkle_tree().
> 
> So, the purpose of this function is unclear.
> 
> Perhaps it should be a prerequisite for all _fsv_scratch_corrupt*() functions,
> and btrfs/290 should check for btrfs-corrupt-block directly?

My intent was for it to be a requirement for _fsv_scratch_corrupt_bytes
and _fsv_scratch_corrupt_merkle_tree, but I missed 576, since I was
testing with btrfs and that doesn't have transparent encryption. Apologies
for missing that test. I'll make _require_fsverity_corruption 1:1 with
_fsv_scratch_corrupt_bytes. However, I believe I still need
btrfs_corrupt_block here, since that is part of the "generic" corruption
for btrfs.

> 
> - Eric

Re: [PATCH v6 4/4] generic: test fs-verity EFBIG scenarios

[Boris Burkov]

On Tue, Mar 15, 2022 at 02:16:30AM +0000, Eric Biggers wrote:
> On Mon, Feb 14, 2022 at 04:09:58PM -0800, Boris Burkov wrote:
> > diff --git a/tests/generic/690 b/tests/generic/690
> > new file mode 100755
> > index 00000000..77906dd8
> > --- /dev/null
> > +++ b/tests/generic/690
> > @@ -0,0 +1,66 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2021 Facebook, Inc.  All Rights Reserved.
> > +#
> > +# FS QA Test 690
> > +#
> > +# fs-verity requires the filesystem to decide how it stores the Merkle tree,
> > +# which can be quite large.
> > +# It is convenient to treat the Merkle tree as past EOF, and ext4, f2fs, and
> > +# btrfs do so in at least some fashion. This leads to an edge case where a
> > +# large file can be under the file system file size limit, but trigger EFBIG
> > +# on enabling fs-verity. Test enabling verity on some large files to exercise
> > +# EFBIG logic for filesystems with fs-verity specific limits.
> > +#
> > +. ./common/preamble
> > +_begin_fstest auto quick verity
> > +
> > +
> > +# Import common functions.
> > +. ./common/filter
> > +. ./common/verity
> > +
> > +# real QA test starts here
> > +_supported_fs generic
> > +_require_test
> > +_require_math
> > +_require_scratch_verity
> > +_require_fsverity_max_file_size_limit
> > +_require_scratch_nocheck
> 
> Why is _require_scratch_nocheck() needed?  _require_scratch_verity() already
> does _require_scratch(), and I don't see why skipping fsck would be needed.
> 
> > +# have to go back by 4096 from max to not hit the fsverity MAX_LEVELS check.
> > +truncate -s $max_sz $fsv_file
> 
> The above comment should be removed.
> 

Thanks for catching these oversights, will fix them. The nocheck thing
was left over from mixing/copy-pasting with btrfs/290 during this test's
evolution. Works fine without it on ext4 and btrfs.

> - Eric