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 2008 [003] 1475.127209: probe:xfs_inode_to_disk: (ffffffffa43fb6b0) if_nextents=98511 i_ino=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_iext_count_may_overflow()) 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-v4. I have a patch that defines the newly introduced error injection tag in xfsprogs (https://github.com/chandanr/xfsprogs-dev/commit/7fd7aeef1cefbcc9abd6dd5887e710c80e48079d). I have also written tests (https://paste.debian.net/1164261/) for verifying the checks introduced in the kernel. The tests have to be edited to make them suitable for merging with xfstests. But they also depend on the changes introduced in xfs_bmap_add_extent_hole_real() and xfs_growfs_rt_alloc(). Hence, I am planning to post the changes for xfsprogs and xfstests if other developers are fine with the changes made to the previously listed functions. Changelog: V3 -> V4: 1. Introduce new patch which lets userspace programs to test "extent count overflow detection" by injecting an error tag. The new error tag reduces the maximum allowed extent count to 10. 2. Injecting the newly defined error tag prevents xfs_bmap_add_extent_hole_real() from merging a new extent with its neighbours to allow writing deterministic tests for testing extent count overflow for Directories, Xattr and growing realtime devices. This is required because the new extent being allocated can be contiguous with its neighbours (w.r.t both file and disk offsets). 3. Injecting the newly defined error tag forces block sized extents to be allocated for summary/bitmap files when growing a realtime device. This is required because xfs_growfs_rt_alloc() allocates as large an extent as possible for summary/bitmap files and hence it would be impossible to write deterministic tests. 4. Rename XFS_IEXT_REMOVE_CNT to XFS_IEXT_PUNCH_HOLE_CNT to reflect the actual meaning of the fs operation. 5. Fold XFS_IEXT_INSERT_HOLE_CNT code into that associated with XFS_IEXT_PUNCH_HOLE_CNT since both perform the same job. 6. xfs_swap_extent_rmap(): Check for extent overflow should be made on the source file only if the donor file extent has a valid on-disk mapping and vice versa. V2 -> V3: 1. Move the definition of xfs_iext_count_may_overflow() from libxfs/xfs_trans_resv.c to libxfs/xfs_inode_fork.c. Also, I tried to make xfs_iext_count_may_overflow() an inline function by placing the definition in libxfs/xfs_inode_fork.h. However this required that the definition of 'struct xfs_inode' be available, since xfs_iext_count_may_overflow() uses a 'struct xfs_inode *' type variable. 2. Handle XFS_COW_FORK within xfs_iext_count_may_overflow() by returning a success value. 3. Rename XFS_IEXT_ADD_CNT to XFS_IEXT_ADD_NOSPLIT_CNT. Thanks to Darrick for the suggesting the new name. 4. Expand comments to make use of 80 columns. V1 -> V2: 1. Rename helper function from xfs_trans_resv_ext_cnt() to xfs_iext_count_may_overflow(). 2. Define and use macros to represent fs operations and the corresponding increase in extent count. 3. Split the patches based on the fs operation being performed. Chandan Babu R (10): xfs: Add helper for checking per-inode extent count overflow xfs: Check for extent overflow when trivally adding a new extent xfs: Check for extent overflow when punching a hole xfs: Check for extent overflow when adding/removing xattrs xfs: Check for extent overflow when adding/removing dir entries xfs: Check for extent overflow when writing to unwritten extent xfs: Check for extent overflow when moving extent from cow to data fork xfs: Check for extent overflow when remapping an extent xfs: Check for extent overflow when swapping extents xfs: Introduce error injection to reduce maximum inode fork extent count fs/xfs/libxfs/xfs_attr.c | 13 ++++++ fs/xfs/libxfs/xfs_bmap.c | 33 ++++++++++----- fs/xfs/libxfs/xfs_bmap.h | 1 + fs/xfs/libxfs/xfs_errortag.h | 4 +- fs/xfs/libxfs/xfs_inode_fork.c | 27 ++++++++++++ fs/xfs/libxfs/xfs_inode_fork.h | 77 ++++++++++++++++++++++++++++++++++ fs/xfs/libxfs/xfs_types.h | 1 + fs/xfs/xfs_bmap_item.c | 5 +++ fs/xfs/xfs_bmap_util.c | 32 ++++++++++++++ fs/xfs/xfs_dquot.c | 8 +++- fs/xfs/xfs_error.c | 3 ++ fs/xfs/xfs_inode.c | 27 ++++++++++++ fs/xfs/xfs_iomap.c | 10 +++++ fs/xfs/xfs_reflink.c | 10 +++++ fs/xfs/xfs_rtalloc.c | 21 +++++++++- fs/xfs/xfs_symlink.c | 5 +++ 16 files changed, 262 insertions(+), 15 deletions(-) -- 2.28.0
