Re: [PATCH v2] xfs: Regression test for vulnerable directory integrity check

[Eryu Guan <guaneryu@gmail.com>]

On Sun, Jun 03, 2018 at 03:56:55PM -0700, Darrick J. Wong wrote:
> On Sun, Jun 03, 2018 at 09:37:18PM +0800, Eryu Guan wrote:
> > On Wed, May 30, 2018 at 04:53:43PM +0800, Xiao Yang wrote:
> > > If a malicious XFS contains a block+ format directory wherein the
> > > directory inode's core.mode is corrupted, and there are subdirectories
> > > of the corrupted directory, an attempt to traverse up the directory
> > > tree by running xfs_scrub will crash the kernel in __xfs_dir3_data_check.
> > > 
> > > Signed-off-by: Xiao Yang <yangx.jy@cn.fujitsu.com>
> > 
> > Thanks for the update!
> > 
> > > ---
> > >  tests/xfs/448     | 96 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > >  tests/xfs/448.out |  2 ++
> > >  tests/xfs/group   |  1 +
> > >  3 files changed, 99 insertions(+)
> > >  create mode 100755 tests/xfs/448
> > >  create mode 100644 tests/xfs/448.out
> > > 
> > > diff --git a/tests/xfs/448 b/tests/xfs/448
> > > new file mode 100755
> > > index 0000000..9ea9295
> > > --- /dev/null
> > > +++ b/tests/xfs/448
> > > @@ -0,0 +1,96 @@
> > > +#! /bin/bash
> > > +# FS QA Test No. 448
> > > +#
> > > +# Regression test for commit:
> > > +# 46c59736d809 ("xfs: harden directory integrity checks some more")
> > 
> > But I couldn't triger the test failre (kernel crash?) with this commit
> > reverted, with either v1 nor v2 patch. I was testing with 4.17-rc5 based
> > kernel, could you please take a look?
> > 
> > > +#
> > > +# If a malicious XFS contains a block+ format directory wherein
> > > +# the directory inode's core.mode is corrupted, and there are
> > > +# subdirectories of the corrupted directory, an attempt to traverse
> > > +# up the directory tree by running xfs_scrub will crash the
> > > +# kernel in __xfs_dir3_data_check.
> > > +#
> > > +# Notice:
> > > +# we should have non fatal asserts configured, because assert
> > > +# failures triggered by the intentional corrupt would crash system.
> > > +#
> > > +#-----------------------------------------------------------------------
> > > +# Copyright (c) 2018 FUJITSU LIMITED. All Rights Reserved.
> > > +#
> > > +# This program is free software; you can redistribute it and/or
> > > +# modify it under the terms of the GNU General Public License as
> > > +# published by the Free Software Foundation.
> > > +#
> > > +# This program is distributed in the hope that it would be useful,
> > > +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> > > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > > +# GNU General Public License for more details.
> > > +#
> > > +# You should have received a copy of the GNU General Public License
> > > +# along with this program; if not, write the Free Software Foundation,
> > > +# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
> > > +#-----------------------------------------------------------------------
> > > +
> > > +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()
> > > +{
> > > +	cd /
> > > +	rm -rf $tmp.*
> > > +}
> > > +
> > > +# get standard environment, filters and checks
> > > +. ./common/rc
> > > +. ./common/filter
> > > +. ./common/populate
> > > +
> > > +# real QA test starts here
> > > +_supported_os Linux
> > > +_supported_fs xfs
> > > +_require_scratch_nocheck
> > > +_require_xfs_io_command "scrub"
> > > +# Corrupt XFS on purpose, and skip if assert failures would crash system.
> > > +_require_no_xfs_bug_on_assert
> > > +
> > > +rm -f "$seqres.full"
> > > +
> > > +# Format and mount
> > > +_scratch_mkfs | _filter_mkfs > $seqres.full 2> $tmp.mkfs || _fail "mkfs failed"
> > > +_scratch_mount
> > > +
> > > +# Get directory block size
> > > +. $tmp.mkfs
> > > +
> > > +# Create a block+(e.g. leaf) format directory
> > > +__populate_create_dir "${SCRATCH_MNT}/dir_leaf" "$((dirbsize / 12))"
> > > +
> > > +# Get the block+ directory inode and a subdirectory inode of it
> > > +subdino=$(stat -c "%i" "$(find ${SCRATCH_MNT}/dir_leaf/* -type d | head -1)")
> > > +dino=$(stat -c "%i" "${SCRATCH_MNT}/dir_leaf")
> > > +
> > > +# Get the subdirectory's generation number
> > > +_scratch_unmount
> > > +subdgen=$(_scratch_xfs_get_metadata_field "core.gen" "inode $subdino")
> > > +
> > > +# Corrupt the directory inode's core.mode
> > > +setmode="0100755"
> > > +_scratch_xfs_set_metadata_field "core.mode" "$setmode" "inode $dino" >> $seqres.full
> > > +getmode=$(_scratch_xfs_get_metadata_field "core.mode" "inode $dino")
> > > +[ "$getmode" != "$setmode" ] && _fail "failed to set core.mode"
> > > +
> > > +# Scrub parent directory in subdirectory (online)
> > > +_scratch_mount
> > > +$XFS_IO_PROG -x -c "scrub parent $subdino $subdgen" ${SCRATCH_MNT} >> $seqres.full
> > 
> > And I always see "+scrub: Inappropriate ioctl for device" here with this
> > v2 patch.
> 
> Your kernel probably needs CONFIG_XFS_ONLINE_SCRUB=y

Yeah, I didn't have XFS_ONLINE_SCRUB enabled..

> 
> This test probably needs:
> 
> . ./config/fuzzy
> _supports_xfs_scrub || _fail "scrub not supported"
> 
> (or make a _requires_xfs_scrub_enabled helper to encapsulate that?)

I thought it was already handled by "_require_xfs_io_command 'scrub'",
(And I think it should be).

I noticed that in _require_xfs_io_command we do

$XFS_IO_PROG -x -c "$command probe 0" $TEST_DIR

which results in:
[root@fedoravm xfstests]# xfs_io -c "scrub probe 0 " /mnt/scratch/
No parameters allowed.

but in _supports_xfs_scrub we do

$XFS_IO_PROG -c "scrub probe" "$mountpoint"

which results in:
[root@fedoravm xfstests]# xfs_io -c "scrub probe " /mnt/scratch/
scrub: Inappropriate ioctl for device

_require_xfs_io_command should be updated?

Thanks,
Eryu
> 
> --D
> 
> > 
> > Thanks,
> > Eryu
> > 
> > > +
> > > +echo "Silence is golden"
> > > +
> > > +# success, all done
> > > +status=0
> > > +exit
> > > diff --git a/tests/xfs/448.out b/tests/xfs/448.out
> > > new file mode 100644
> > > index 0000000..b6f0a53
> > > --- /dev/null
> > > +++ b/tests/xfs/448.out
> > > @@ -0,0 +1,2 @@
> > > +QA output created by 448
> > > +Silence is golden
> > > diff --git a/tests/xfs/group b/tests/xfs/group
> > > index 51326d9..dd39d08 100644
> > > --- a/tests/xfs/group
> > > +++ b/tests/xfs/group
> > > @@ -445,3 +445,4 @@
> > >  445 auto quick filestreams
> > >  446 auto quick
> > >  447 auto mount
> > > +448 auto quick fuzzers
> > > -- 
> > > 1.8.3.1
> > > 
> > > 
> > >