CVE-2024-26704 Information

Apr 04, 2024 cve

Description

In the Linux kernel the following vulnerability has been resolved:

ext4: fix double-free of blocks due to wrong extents moved_len

In ext4_move_extents() moved_len is only updated when all moves are successfully executed and only discards orig_inode and donor_inode preallocations when moved_len is not zero. When the loop fails to exit after successfully moving some extents moved_len is not updated and remains at 0 so it does not discard the preallocations.

If the moved extents overlap with the preallocated extents the overlapped extents are freed twice in ext4_mb_release_inode_pa() and ext4_process_freed_data() (as described in commit 94d7c16cbbbd (xt4: Fix double-free of blocks with EXT4_IOC_MOVE_EXT)) and bb_free is incremented twice. Hence when trim is executed a zero-division bug is triggered in mb_update_avg_fragment_size() because bb_free is not zero and bb_fragments is zero.

Therefore update move_len after each extent move to avoid the issue.

Reference

Share on: