XFS does not check for possible overflow of per-inode extent counter fields when adding extents to either data or attr fork. For e.g. 1. Insert 5 million xattrs (each having a value size of 255 bytes) and then delete 50% of them in an alternating manner. 2. On a 4k block sized XFS filesystem instance, the above causes 98511 extents to be created in the attr fork of the inode. xfsaild/loop0 2035 [003] 9643.390490: probe:xfs_iflush_int: (ffffffffac6225c0) if_nextents=98511 inode=131 3. The incore inode fork extent counter is a signed 32-bit quantity. However the on-disk extent counter is an unsigned 16-bit quantity and hence cannot hold 98511 extents. 4. The following incorrect value is stored in the xattr extent counter, # xfs_db -f -c 'inode 131' -c 'print core.naextents' /dev/loop0 core.naextents = -32561 This patchset adds a new helper function (i.e. xfs_trans_resv_ext_cnt()) to check for overflow of the per-inode data and xattr extent counters and invokes it before starting an fs operation (e.g. creating a new directory entry). With this patchset applied, XFS detects counter overflows and returns with an error rather than causing a silent corruption. The patchset has been tested by executing xfstests with the following mkfs.xfs options, 1. -m crc=0 -b size=1k 2. -m crc=0 -b size=4k 3. -m crc=0 -b size=512 4. -m rmapbt=1,reflink=1 -b size=1k 5. -m rmapbt=1,reflink=1 -b size=4k The patches can also be obtained from https://github.com/chandanr/linux.git at branch xfs-reserve-extent-count-v0. PS: I am planning to write the code which extends data/xattr extent counters from 32-bit/16-bit to 64-bit/32-bit on top of these patches. fs/xfs/libxfs/xfs_attr.c | 33 ++++++++++-- fs/xfs/libxfs/xfs_bmap.c | 7 +++ fs/xfs/libxfs/xfs_trans_resv.c | 33 ++++++++++++ fs/xfs/libxfs/xfs_trans_resv.h | 1 + fs/xfs/xfs_bmap_item.c | 12 +++++ fs/xfs/xfs_bmap_util.c | 40 ++++++++++++++ fs/xfs/xfs_dquot.c | 7 ++- fs/xfs/xfs_inode.c | 96 ++++++++++++++++++++++++++++++++++ fs/xfs/xfs_iomap.c | 19 +++++++ fs/xfs/xfs_reflink.c | 35 +++++++++++++ fs/xfs/xfs_rtalloc.c | 4 ++ fs/xfs/xfs_symlink.c | 18 +++++++ 12 files changed, 301 insertions(+), 4 deletions(-) -- 2.27.0
