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@berkeley.edu>
Fixes: da5e7c87827e ("ocfs2: cleanup journal init and shutdown")
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Tested-by: Farhad Alemi <farhad.alemi@berkeley.edu>
---
 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;
+
 	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

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@berkeley.edu>
> Fixes: da5e7c87827e ("ocfs2: cleanup journal init and shutdown")
> Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> Tested-by: Farhad Alemi <farhad.alemi@berkeley.edu>

LGTM.
Reviewed-by: Heming Zhao <heming.zhao@suse.com>

> ---
>  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;
> +
>  	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
>

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@berkeley.edu>
> Fixes: da5e7c87827e ("ocfs2: cleanup journal init and shutdown")
> Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> Tested-by: Farhad Alemi <farhad.alemi@berkeley.edu>
> ---
>  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
>

On 6/1/26 11:32 AM, Heming Zhao wrote:
> 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@berkeley.edu>
>> Fixes: da5e7c87827e ("ocfs2: cleanup journal init and shutdown")
>> Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
>> Tested-by: Farhad Alemi <farhad.alemi@berkeley.edu>
>> ---
>>  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.
> 
During unmount, journal shutdown happens before final inode eviction is 
triggered by generic_shutdown_super() -> evict_inodes(). That means they
run sequentially in the unmount path (same thread context).

Thanks,
Joseph

On Mon, Jun 01, 2026 at 02:50:56PM +0800, Joseph Qi wrote:
> 
> 
> On 6/1/26 11:32 AM, Heming Zhao wrote:
> > 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@berkeley.edu>
> >> Fixes: da5e7c87827e ("ocfs2: cleanup journal init and shutdown")
> >> Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
> >> Tested-by: Farhad Alemi <farhad.alemi@berkeley.edu>
> >> ---
> >>  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.
> > 
> During unmount, journal shutdown happens before final inode eviction is 
> triggered by generic_shutdown_super() -> evict_inodes(). That means they
> run sequentially in the unmount path (same thread context).
> 
> Thanks,
> Joseph
> 

Thanks for the explanation. I will provide my Reviewed-by tag.

Based on the call stack in Farhad's email attachment, it seems the test case
triggered the if (osb->slot_num != OCFS2_INVALID_SLOT) condition in
ocfs2_dismount_volume() to skip the released slot_inode.

Thanks,
Heming