| Sažetak |
In the Linux kernel, the following vulnerability has been resolved:
ocfs2: clear extent cache after moving/defragmenting extents
The extent map cache can become stale when extents are moved or
defragmented, causing subsequent operations to see outdated extent flags.
This triggers a BUG_ON in ocfs2_refcount_cal_cow_clusters().
The problem occurs when:
1. copy_file_range() creates a reflinked extent with OCFS2_EXT_REFCOUNTED
2. ioctl(FITRIM) triggers ocfs2_move_extents()
3. __ocfs2_move_extents_range() reads and caches the extent (flags=0x2)
4. ocfs2_move_extent()/ocfs2_defrag_extent() calls __ocfs2_move_extent()
which clears OCFS2_EXT_REFCOUNTED flag on disk (flags=0x0)
5. The extent map cache is not invalidated after the move
6. Later write() operations read stale cached flags (0x2) but disk has
updated flags (0x0), causing a mismatch
7. BUG_ON(!(rec->e_flags & OCFS2_EXT_REFCOUNTED)) triggers
Fix by clearing the extent map cache after each extent move/defrag
operation in __ocfs2_move_extents_range(). This ensures subsequent
operations read fresh extent data from disk. |
