Re: [PATCH] ocfs2: add journal NULL check in ocfs2_checkpoint_inode()

[Heming Zhao]

On Sun, May 31, 2026 at 09:16:45PM +0800, Joseph Qi wrote:
> During unmount, ocfs2_journal_shutdown() frees the journal and sets
> osb->journal to NULL. Later, when VFS evicts remaining cached inodes,
> ocfs2_evict_inode() -> ocfs2_clear_inode() -> ocfs2_checkpoint_inode()
> -> ocfs2_ci_fully_checkpointed() dereferences osb->journal, causing a
> NULL pointer dereference.
> 
> Fix this by adding a NULL check for osb->journal in
> ocfs2_checkpoint_inode(). If the journal is NULL, it has already been
> fully flushed and destroyed during shutdown, so there is nothing to
> checkpoint.
> 
> Reported-by: Farhad Alemi <farhad.alemi@xxxxxxxxxxxx>
> Fixes: da5e7c87827e ("ocfs2: cleanup journal init and shutdown")
> Signed-off-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
> Tested-by: Farhad Alemi <farhad.alemi@xxxxxxxxxxxx>
> ---
>  fs/ocfs2/journal.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/ocfs2/journal.h b/fs/ocfs2/journal.h
> index 6397170f302f..f8b3b2a3d630 100644
> --- a/fs/ocfs2/journal.h
> +++ b/fs/ocfs2/journal.h
> @@ -196,6 +196,9 @@ static inline void ocfs2_checkpoint_inode(struct inode *inode)
>  	if (ocfs2_mount_local(osb))
>  		return;
>  
> +	if (!osb->journal)
> +		return;
> +

In my view, the code is correct for this bug.
However, the if condition is insufficient if ocfs2_journal_shutdown() sets
"journal = NULL" immediately after this line.

Thanks,
Heming
>  	if (!ocfs2_ci_fully_checkpointed(INODE_CACHE(inode))) {
>  		/* WARNING: This only kicks off a single
>  		 * checkpoint. If someone races you and adds more
> -- 
> 2.39.3
>