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-v14. I have two patches that define the newly introduced error injection tags in xfsprogs (https://lore.kernel.org/linux-xfs/20201104114900.172147-1-chandanrlinux@xxxxxxxxx/). I have also written tests (https://github.com/chandanr/xfstests/commits/extent-overflow-tests) for verifying the checks introduced in the kernel. Changelog: V13 -> V14: 1. Fix incorrect comparison of xfs_iext_count_may_overflow()'s return value with -ENOSPC in xfs_bmap_del_extent_real(). Also, for quick reference, the following are the patches that need to be reviewed, - [PATCH V14 04/16] xfs: Check for extent overflow when adding dir entries - [PATCH V14 05/16] xfs: Check for extent overflow when removing dir entries - [PATCH V14 06/16] xfs: Check for extent overflow when renaming dir entries V12 -> V13: 1. xfs_rename(): - Add comment explaining why we do not check for extent count overflow for the source directory entry of a rename operation. - Fix grammatical nit in a comment. 2. xfs_bmap_del_extent_real(): Replace explicit checks for inode's mode and fork with an assert() call since extent count overflow check here is applicable only to directory entry remove/rename operation. V11 -> V12: 1. Rebase patches on top of Linux v5.11-rc1. 2. Revert back to using using a pseudo max inode extent count of 10. Hence the patches - [PATCH V12 05/14] xfs: Check for extent overflow when adding/removing xattrs - [PATCH V12 10/14] xfs: Introduce error injection to reduce maximum have been reverted back (including retaining of corresponding RVB tags) to how it was under V10 of the patchset. V11 of the patchset had increased the max pseudo extent count to 35 to allow for "directory entry remove" operation to always succeed. However the corresponding logic was incorrect. Please refer to "[PATCH V12 04/14] xfs: Check for extent overflow when adding/removing dir entries" to find logic and explaination of the newer logic. "[PATCH V12 04/14] xfs: Check for extent overflow when adding/removing dir entries" is the only patch yet to be reviewed. V10 -> V11: 1. For directory/xattr insert operations we now reserve sufficient number of "extent count" so as to guarantee a future directory/xattr remove operation. 2. The pseudo max extent count value has been increased to 35. V9 -> V10: 1. Pull back changes which cause xfs_bmap_compute_alignments() to return "stripe alignment" into 12th patch i.e. "xfs: Compute bmap extent alignments in a separate function". V8 -> V9: 1. Enabling XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT error tag will always allocate single block sized free extents (if available). 2. xfs_bmap_compute_alignments() now returns stripe alignment as its return value. 3. Dropped Allison's RVB tag for "xfs: Compute bmap extent alignments in a separate function" and "xfs: Introduce error injection to allocate only minlen size extents for files". V7 -> V8: 1. Rename local variable in xfs_alloc_fix_freelist() from "i" to "stat". V6 -> V7: 1. Create new function xfs_bmap_exact_minlen_extent_alloc() (enabled only when CONFIG_XFS_DEBUG is set to y) which issues allocation requests for minlen sized extents only. In order to achieve this, common code from xfs_bmap_btalloc() have been refactored into new functions. 2. All major functions implementing logic associated with XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT error tag are compiled only when CONFIG_XFS_DEBUG is set to y. 3. Remove XFS_IEXT_REFLINK_REMAP_CNT macro and replace it with an integer which holds the number of new extents to be added to the data fork. V5 -> V6: 1. Rebased the patchset on xfs-linux/for-next branch. 2. Drop "xfs: Set tp->t_firstblock only once during a transaction's lifetime" patch from the patchset. 3. Add a comment to xfs_bmap_btalloc() describing why it was chosen to start "free space extent search" from AG 0 when XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT is enabled and when the transaction is allocating its first extent. 4. Fix review comments associated with coding style. V4 -> V5: 1. Introduce new error tag XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT to let user space programs to be able to guarantee that free space requests for files are satisfied by allocating minlen sized extents. 2. Change xfs_bmap_btalloc() and xfs_alloc_vextent() to allocate minlen sized extents when XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT is enabled. 3. Introduce a new patch that causes tp->t_firstblock to be assigned to a value only when its previous value is NULLFSBLOCK. 4. Replace the previously introduced MAXERRTAGEXTNUM (maximum inode fork extent count) with the hardcoded value of 10. 5. xfs_bui_item_recover(): Use XFS_IEXT_ADD_NOSPLIT_CNT when mapping an extent. 6. xfs_swap_extent_rmap(): Use xfs_bmap_is_real_extent() instead of xfs_bmap_is_update_needed() to assess if the extent really needs to be swapped. 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 (16): 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 dir entries xfs: Check for extent overflow when removing dir entries xfs: Check for extent overflow when renaming dir entries xfs: Check for extent overflow when adding/removing xattrs 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 xfs: Remove duplicate assert statement in xfs_bmap_btalloc() xfs: Compute bmap extent alignments in a separate function xfs: Process allocated extent in a separate function xfs: Introduce error injection to allocate only minlen size extents for files fs/xfs/libxfs/xfs_alloc.c | 50 ++++++ fs/xfs/libxfs/xfs_alloc.h | 3 + fs/xfs/libxfs/xfs_attr.c | 13 ++ fs/xfs/libxfs/xfs_bmap.c | 285 ++++++++++++++++++++++++--------- fs/xfs/libxfs/xfs_errortag.h | 6 +- fs/xfs/libxfs/xfs_inode_fork.c | 27 ++++ fs/xfs/libxfs/xfs_inode_fork.h | 63 ++++++++ fs/xfs/xfs_bmap_item.c | 10 ++ fs/xfs/xfs_bmap_util.c | 31 ++++ fs/xfs/xfs_dquot.c | 8 +- fs/xfs/xfs_error.c | 6 + fs/xfs/xfs_inode.c | 54 ++++++- fs/xfs/xfs_iomap.c | 10 ++ fs/xfs/xfs_reflink.c | 16 ++ fs/xfs/xfs_rtalloc.c | 5 + fs/xfs/xfs_symlink.c | 5 + 16 files changed, 513 insertions(+), 79 deletions(-) -- 2.29.2
