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

Vulnerability Description

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.

References

• https://git.kernel.org/stable/c/fd89d92c1140cee8f59de336cb37fa65e359c123
• https://git.kernel.org/stable/c/703b2c7e0798d263154dc8593dc2345f75dc077f
• https://git.kernel.org/stable/c/bf605ae98dab5c15c5b631d4d7f88898cb41b649
• https://git.kernel.org/stable/c/ff55291fb36779819211b596da703389135f5b05
• https://git.kernel.org/stable/c/82dfdd1e31e774578f76ce6dc90c834f96403a0f
• https://git.kernel.org/stable/c/86a89e75e9e4dfa768b97db466ad6bedf2e7ea5b
• https://git.kernel.org/stable/c/f60e94a83db799bde625ac8671a5b4a6354e7120
• https://git.kernel.org/stable/c/387bf565cc03e2e8c720b8b4798efea4aacb6962
• https://git.kernel.org/stable/c/5784d9fcfd43bd853654bb80c87ef293b9e8e80a