[PATCH 14/17] btrfs: handle non-fatal errors in btrfs_qgroup_inherit()

David Sterba
2016-05-05T09:44:40Z

From: Mark Fasheh <mfasheh@suse.de>

create_pending_snapshot() will go readonly on _any_ error return from
btrfs_qgroup_inherit(). If qgroups are enabled, a user can crash their fs by
just making a snapshot and asking it to inherit from an invalid qgroup. For
example:

$ btrfs sub snap -i 1/10 /btrfs/ /btrfs/foo

Will cause a transaction abort.

Fix this by only throwing errors in btrfs_qgroup_inherit() when we know
going readonly is acceptable.

The following xfstests test case reproduces this bug:

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 -f $tmp.*
}

# get standard environment, filters and checks
. ./common/rc
. ./common/filter

# remove previous $seqres.full before test
rm -f $seqres.full

# real QA test starts here
_supported_fs btrfs
_supported_os Linux
_require_scratch

rm -f $seqres.full

_scratch_mkfs
_scratch_mount
_run_btrfs_util_prog quota enable $SCRATCH_MNT
# The qgroup '1/10' does not exist and should be silently ignored
_run_btrfs_util_prog subvolume snapshot -i 1/10 $SCRATCH_MNT $SCRATCH_MNT/snap1

_scratch_unmount

echo "Silence is golden"

status=0
exit

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Reviewed-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/qgroup.c | 54 ++++++++++++++++++++++++++++++++----------------------
1 file changed, 32 insertions(+), 22 deletions(-)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 5279fdae7142..7173360eea7a 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1842,8 +1842,10 @@ int btrfs_run_qgroups(struct btrfs_trans_handle *trans,
}

/*
- * copy the acounting information between qgroups. This is necessary when a
- * snapshot or a subvolume is created
+ * Copy the acounting information between qgroups. This is necessary
+ * when a snapshot or a subvolume is created. Throwing an error will
+ * cause a transaction abort so we take extra care here to only error
+ * when a readonly fs is a reasonable outcome.
*/
int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 srcid, u64 objectid,
@@ -1873,15 +1875,15 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
2 * inherit->num_excl_copies;
for (i = 0; i < nums; ++i) {
srcgroup = find_qgroup_rb(fs_info, *i_qgroups);
- if (!srcgroup) {
- ret = -EINVAL;
- goto out;
- }

- if ((srcgroup->qgroupid >> 48) <= (objectid >> 48)) {
- ret = -EINVAL;
- goto out;
- }
+ /*
+ * Zero out invalid groups so we can ignore
+ * them later.
+ */
+ if (!srcgroup ||
+ ((srcgroup->qgroupid >> 48) <= (objectid >> 48)))
+ *i_qgroups = 0ULL;
+
++i_qgroups;
}
}
@@ -1916,17 +1918,19 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
*/
if (inherit) {
i_qgroups = (u64 *)(inherit + 1);
- for (i = 0; i < inherit->num_qgroups; ++i) {
+ for (i = 0; i < inherit->num_qgroups; ++i, ++i_qgroups) {
+ if (*i_qgroups == 0)
+ continue;
ret = add_qgroup_relation_item(trans, quota_root,
objectid, *i_qgroups);
- if (ret)
+ if (ret && ret != -EEXIST)
goto out;
ret = add_qgroup_relation_item(trans, quota_root,
*i_qgroups, objectid);
- if (ret)
+ if (ret && ret != -EEXIST)
goto out;
- ++i_qgroups;
}
+ ret = 0;
}

@@ -1987,17 +1991,22 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,

i_qgroups = (u64 *)(inherit + 1);
for (i = 0; i < inherit->num_qgroups; ++i) {
- ret = add_relation_rb(quota_root->fs_info, objectid,
- *i_qgroups);
- if (ret)
- goto unlock;
+ if (*i_qgroups) {
+ ret = add_relation_rb(quota_root->fs_info, objectid,
+ *i_qgroups);
+ if (ret)
+ goto unlock;
+ }
++i_qgroups;
}

- for (i = 0; i < inherit->num_ref_copies; ++i) {
+ for (i = 0; i < inherit->num_ref_copies; ++i, i_qgroups += 2) {
struct btrfs_qgroup *src;
struct btrfs_qgroup *dst;

+ if (!i_qgroups[0] || !i_qgroups[1])
+ continue;
+
src = find_qgroup_rb(fs_info, i_qgroups[0]);
dst = find_qgroup_rb(fs_info, i_qgroups[1]);

@@ -2008,12 +2017,14 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,

dst->rfer = src->rfer - level_size;
dst->rfer_cmpr = src->rfer_cmpr - level_size;
- i_qgroups += 2;
}
- for (i = 0; i < inherit->num_excl_copies; ++i) {
+ for (i = 0; i < inherit->num_excl_copies; ++i, i_qgroups += 2) {
struct btrfs_qgroup *src;
struct btrfs_qgroup *dst;

+ if (!i_qgroups[0] || !i_qgroups[1])
+ continue;
+
src = find_qgroup_rb(fs_info, i_qgroups[0]);
dst = find_qgroup_rb(fs_info, i_qgroups[1]);

@@ -2024,7 +2035,6 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,

dst->excl = src->excl + level_size;
dst->excl_cmpr = src->excl_cmpr + level_size;
- i_qgroups += 2;
}

unlock:
--
2.7.1