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author | Akira Fujita <a-fujita@rs.jp.nec.com> | 2009-11-24 10:19:57 -0500 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2009-11-24 10:19:57 -0500 |
commit | 94d7c16cbbbd0e03841fcf272bcaf0620ad39618 (patch) | |
tree | 12a4d8b28bd5bf338b9bd1874e18d4bfdc77837a /Documentation/cris | |
parent | 9084d4719784b00ff0bf9c9580007fac8277dbcb (diff) | |
download | blackbird-op-linux-94d7c16cbbbd0e03841fcf272bcaf0620ad39618.tar.gz blackbird-op-linux-94d7c16cbbbd0e03841fcf272bcaf0620ad39618.zip |
ext4: Fix double-free of blocks with EXT4_IOC_MOVE_EXT
At the beginning of ext4_move_extent(), we call
ext4_discard_preallocations() to discard inode PAs of orig and donor
inodes. But in the following case, blocks can be double freed, so
move ext4_discard_preallocations() to the end of ext4_move_extents().
1. Discard inode PAs of orig and donor inodes with
ext4_discard_preallocations() in ext4_move_extents().
orig : [ DATA1 ]
donor: [ DATA2 ]
2. While data blocks are exchanging between orig and donor inodes, new
inode PAs is created to orig by other process's block allocation.
(Since there are semaphore gaps in ext4_move_extents().) And new
inode PAs is used partially (2-1).
2-1 Create new inode PAs to orig inode
orig : [ DATA1 | used PA1 | free PA1 ]
donor: [ DATA2 ]
3. Donor inode which has old orig inode's blocks is deleted after
EXT4_IOC_MOVE_EXT finished (3-1, 3-2). So the block bitmap
corresponds to old orig inode's blocks are freed.
3-1 After EXT4_IOC_MOVE_EXT finished
orig : [ DATA2 | free PA1 ]
donor: [ DATA1 | used PA1 ]
3-2 Delete donor inode
orig : [ DATA2 | free PA1 ]
donor: [ FREE SPACE(DATA1) | FREE SPACE(used PA1) ]
4. The double-free of blocks is occurred, when close() is called to
orig inode. Because ext4_discard_preallocations() for orig inode
frees used PA1 and free PA1, though used PA1 is already freed in 3.
4-1 Double-free of blocks is occurred
orig : [ DATA2 | FREE SPACE(free PA1) ]
donor: [ FREE SPACE(DATA1) | DOUBLE FREE(used PA1) ]
Signed-off-by: Akira Fujita <a-fujita@rs.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'Documentation/cris')
0 files changed, 0 insertions, 0 deletions