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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 | Greg Kroah-Hartman <gregkh@suse.de> | 2009-12-14 09:45:07 -0800 |
commit | 74920c74ad3802bc81f5ccbb737d351073dd3ff9 (patch) | |
tree | 76d5ca0e8d519540e127e390d514ebb246cf74c3 /fs/binfmt_flat.c | |
parent | 6011d0baad8d5229445b1e0f7b6bdfcaf9cbff26 (diff) |
ext4: Fix double-free of blocks with EXT4_IOC_MOVE_EXT
(cherry picked from commit 94d7c16cbbbd0e03841fcf272bcaf0620ad39618)
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'fs/binfmt_flat.c')
0 files changed, 0 insertions, 0 deletions