Re: [Ocfs2-devel] [PATCH 2/3] fs: ocfs2: Fix a possible null-pointer dereference in ocfs2_write_end_nolock()

[Changwei Ge]

Hi Jia-ju,


Could you please point out how ->w_handle can be NULL if we are changing 
disk inode?

I just checked the ocfs2 code but can't find any clue ...

In my opinion, it's impossible to change disk inode without an existed 
journal transaction. If truly so, it's a another problem.


Thanks,

Changwei


On 2019/7/26 5:38 äå, Joseph Qi wrote:
> On 19/7/26 11:37, Jia-Ju Bai wrote:
> > In ocfs2_write_end_nolock(), there are an if statement on lines 1976,
> > 2047 and 2058, to check whether handle is NULL:
> >      if (handle)
> >
> > When handle is NULL, it is used on line 2045:
> > 	ocfs2_update_inode_fsync_trans(handle, inode, 1);
> >          oi->i_sync_tid = handle->h_transaction->t_tid;
> >
> > Thus, a possible null-pointer dereference may occur.
> >
> > To fix this bug, handle is checked before calling
> > ocfs2_update_inode_fsync_trans().
> >
> > This bug is found by a static analysis tool STCheck written by us.
> >
> > Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
> Looks good.
> Reviewed-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
>
> > ---
> >   fs/ocfs2/aops.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
> > index a4c905d6b575..5473bd99043e 100644
> > --- a/fs/ocfs2/aops.c
> > +++ b/fs/ocfs2/aops.c
> > @@ -2042,7 +2042,8 @@ int ocfs2_write_end_nolock(struct address_space *mapping,
> >   		inode->i_mtime = inode->i_ctime = current_time(inode);
> >   		di->i_mtime = di->i_ctime = cpu_to_le64(inode->i_mtime.tv_sec);
> >   		di->i_mtime_nsec = di->i_ctime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
> > -		ocfs2_update_inode_fsync_trans(handle, inode, 1);
> > +		if (handle)
> > +			ocfs2_update_inode_fsync_trans(handle, inode, 1);
> >   	}
> >   	if (handle)
> >   		ocfs2_journal_dirty(handle, wc->w_di_bh);
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