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authorAkira Fujita <a-fujita@rs.jp.nec.com>2009-11-24 10:19:57 -0500
committerTheodore Ts'o <tytso@mit.edu>2009-11-24 10:19:57 -0500
commit94d7c16cbbbd0e03841fcf272bcaf0620ad39618 (patch)
tree12a4d8b28bd5bf338b9bd1874e18d4bfdc77837a
parent9084d4719784b00ff0bf9c9580007fac8277dbcb (diff)
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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>
-rw-r--r--fs/ext4/move_extent.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 5a106e0..3478889 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -1289,10 +1289,6 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
ext4_ext_get_actual_len(ext_cur), block_end + 1) -
max(le32_to_cpu(ext_cur->ee_block), block_start);
- /* Discard preallocations of two inodes */
- ext4_discard_preallocations(orig_inode);
- ext4_discard_preallocations(donor_inode);
-
while (!last_extent && le32_to_cpu(ext_cur->ee_block) <= block_end) {
seq_blocks += add_blocks;
@@ -1410,6 +1406,11 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp,
}
out:
+ if (*moved_len) {
+ ext4_discard_preallocations(orig_inode);
+ ext4_discard_preallocations(donor_inode);
+ }
+
if (orig_path) {
ext4_ext_drop_refs(orig_path);
kfree(orig_path);