[SRU][M][PATCH 0/1] CVE-2024-26704

[Bethany Jamison]

[Impact]

 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 ("ext4:
 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.

[Fix]

Mantic:	Clean cherry-pick from linux-6.6.y
Jammy:	pending
Focal:	pending
Bionic:	fix sent to esm ML
Xenial:	fix sent to esm ML
Trusty:	not-affected

[Test Case]

Compile and boot tested.

[Where problems could occur]

This fix affects those who use the Ext4 file system, and an issue with
this fix would be visable to the user via a system crash.

Baokun Li (1):
  ext4: fix double-free of blocks due to wrong extents moved_len

 fs/ext4/move_extent.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

-- 
2.34.1