4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Julian Sun <sunjunchao2870@xxxxxxxxx> commit 5784d9fcfd43bd853654bb80c87ef293b9e8e80a upstream. During the mounting process, if journal_reset() fails because of too short journal, then lead to jbd2_journal_load() fails with NULL j_sb_buffer. Subsequently, ocfs2_journal_shutdown() calls jbd2_journal_flush()->jbd2_cleanup_journal_tail()-> __jbd2_update_log_tail()->jbd2_journal_update_sb_log_tail() ->lock_buffer(journal->j_sb_buffer), resulting in a null-pointer dereference error. To resolve this issue, we should check the JBD2_LOADED flag to ensure the journal was properly loaded. Additionally, use journal instead of osb->journal directly to simplify the code. Link: https://syzkaller.appspot.com/bug?extid=05b9b39d8bdfe1a0861f Link: https://lkml.kernel.org/r/20240902030844.422725-1-sunjunchao2870@xxxxxxxxx Fixes: f6f50e28f0cb ("jbd2: Fail to load a journal if it is too short") Signed-off-by: Julian Sun <sunjunchao2870@xxxxxxxxx> Reported-by: syzbot+05b9b39d8bdfe1a0861f@xxxxxxxxxxxxxxxxxxxxxxxxx Suggested-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx> Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx> Cc: Mark Fasheh <mark@xxxxxxxxxx> Cc: Joel Becker <jlbec@xxxxxxxxxxxx> Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx> Cc: Changwei Ge <gechangwei@xxxxxxx> Cc: Gang He <ghe@xxxxxxxx> Cc: Jun Piao <piaojun@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/ocfs2/journal.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/fs/ocfs2/journal.c +++ b/fs/ocfs2/journal.c @@ -989,7 +989,7 @@ void ocfs2_journal_shutdown(struct ocfs2 if (!igrab(inode)) BUG(); - num_running_trans = atomic_read(&(osb->journal->j_num_trans)); + num_running_trans = atomic_read(&(journal->j_num_trans)); trace_ocfs2_journal_shutdown(num_running_trans); /* Do a commit_cache here. It will flush our journal, *and* @@ -1008,9 +1008,10 @@ void ocfs2_journal_shutdown(struct ocfs2 osb->commit_task = NULL; } - BUG_ON(atomic_read(&(osb->journal->j_num_trans)) != 0); + BUG_ON(atomic_read(&(journal->j_num_trans)) != 0); - if (ocfs2_mount_local(osb)) { + if (ocfs2_mount_local(osb) && + (journal->j_journal->j_flags & JBD2_LOADED)) { jbd2_journal_lock_updates(journal->j_journal); status = jbd2_journal_flush(journal->j_journal); jbd2_journal_unlock_updates(journal->j_journal);
