CVE-2024-49957

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

ocfs2: fix null-ptr-deref when journal load failed.

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.