CVE-2025-22113

In the Linux kernel, the following vulnerability has been resolved:

ext4: avoid journaling sb update on error if journal is destroying

Presently we always BUG_ON if trying to start a transaction on a journal marked with JBD2_UNMOUNT, since this should never happen. However, while ltp running stress tests, it was observed that in case of some error handling paths, it is possible for update_super_work to start a transaction after the journal is destroyed eg:

(umount) ext4_kill_sb kill_block_super generic_shutdown_super sync_filesystem /* commits all txns / evict_inodes / might start a new txn / ext4_put_super flush_work(&sbi->s_sb_upd_work) / flush the workqueue */ jbd2_journal_destroy journal_kill_thread journal->j_flags |= JBD2_UNMOUNT; jbd2_journal_commit_transaction jbd2_journal_get_descriptor_buffer jbd2_journal_bmap ext4_journal_bmap ext4_map_blocks ... ext4_inode_error ext4_handle_error schedule_work(&sbi->s_sb_upd_work)

                                           /* work queue kicks in */
                                           update_super_work
                                             jbd2_journal_start
                                               start_this_handle
                                                 BUG_ON(journal->j_flags &
                                                        JBD2_UNMOUNT)

Hence, introduce a new mount flag to indicate journal is destroying and only do a journaled (and deferred) update of sb if this flag is not set. Otherwise, just fallback to an un-journaled commit.

Further, in the journal destroy path, we have the following sequence:

1. Set mount flag indicating journal is destroying
2. force a commit and wait for it
3. flush pending sb updates

This sequence...