From 94d7c16cbbbd0e03841fcf272bcaf0620ad39618 Mon Sep 17 00:00:00 2001 From: Akira Fujita Date: Tue, 24 Nov 2009 10:19:57 -0500 Subject: [PATCH] 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 Signed-off-by: "Theodore Ts'o" --- fs/ext4/move_extent.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c index 5a106e02fd9c..3478889e00b3 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); -- 2.20.1