From: Qu Wenruo wqu@suse.com
commit d4e204948fe3e0dc8e1fbf3f8f3290c9c2823be3 upstream.
[BUG] The following script can cause btrfs qgroup data space leak:
mkfs.btrfs -f $dev mount $dev -o nospace_cache $mnt
btrfs subv create $mnt/subv btrfs quota en $mnt btrfs quota rescan -w $mnt btrfs qgroup limit 128m $mnt/subv
for (( i = 0; i < 3; i++)); do # Create 3 64M holes for latter fallocate to fail truncate -s 192m $mnt/subv/file xfs_io -c "pwrite 64m 4k" $mnt/subv/file > /dev/null xfs_io -c "pwrite 128m 4k" $mnt/subv/file > /dev/null sync
# it's supposed to fail, and each failure will leak at least 64M # data space xfs_io -f -c "falloc 0 192m" $mnt/subv/file &> /dev/null rm $mnt/subv/file sync done
# Shouldn't fail after we removed the file xfs_io -f -c "falloc 0 64m" $mnt/subv/file
[CAUSE] Btrfs qgroup data reserve code allow multiple reservations to happen on a single extent_changeset: E.g: btrfs_qgroup_reserve_data(inode, &data_reserved, 0, SZ_1M); btrfs_qgroup_reserve_data(inode, &data_reserved, SZ_1M, SZ_2M); btrfs_qgroup_reserve_data(inode, &data_reserved, 0, SZ_4M);
Btrfs qgroup code has its internal tracking to make sure we don't double-reserve in above example.
The only pattern utilizing this feature is in the main while loop of btrfs_fallocate() function.
However btrfs_qgroup_reserve_data()'s error handling has a bug in that on error it clears all ranges in the io_tree with EXTENT_QGROUP_RESERVED flag but doesn't free previously reserved bytes.
This bug has a two fold effect: - Clearing EXTENT_QGROUP_RESERVED ranges This is the correct behavior, but it prevents btrfs_qgroup_check_reserved_leak() to catch the leakage as the detector is purely EXTENT_QGROUP_RESERVED flag based.
- Leak the previously reserved data bytes.
The bug manifests when N calls to btrfs_qgroup_reserve_data are made and the last one fails, leaking space reserved in the previous ones.
[FIX] Also free previously reserved data bytes when btrfs_qgroup_reserve_data fails.
Fixes: 524725537023 ("btrfs: qgroup: Introduce btrfs_qgroup_reserve_data function") CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Qu Wenruo wqu@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/qgroup.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -3067,6 +3067,9 @@ cleanup: while ((unode = ulist_next(&reserved->range_changed, &uiter))) clear_extent_bit(&BTRFS_I(inode)->io_tree, unode->val, unode->aux, EXTENT_QGROUP_RESERVED, 0, 0, NULL); + /* Also free data bytes of already reserved one */ + btrfs_qgroup_free_refroot(root->fs_info, root->root_key.objectid, + orig_reserved, BTRFS_QGROUP_RSV_DATA); extent_changeset_release(reserved); return ret; }