Affected: Linux

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_…