Re: [PATCH] ubifs: Free memory for tmpfile name

[Zhihao Cheng]

Hi Mårten,
> Hi Zhihao!
>
> On 3/30/23 04:25, Zhihao Cheng wrote:
> > Hi Mårten,
> > > When opening a ubifs tmpfile on an encrypted directory, function
> > > fscrypt_setup_filename allocates memory for the name that is to be
> > > stored in the directory entry, but after the name has been copied to the
> > > directory entry inode, the memory is not freed.
> > >
> > > When running kmemleak on it we see that it is registered as a leak. The
> > > report below is triggered by a simple program 'tmpfile' just opening a
> > > tmpfile:
> > >
> > >    unreferenced object 0xffff88810178f380 (size 32):
> > >      comm "tmpfile", pid 509, jiffies 4294934744 (age 1524.742s)
> > >      backtrace:
> > >        __kmem_cache_alloc_node
> > >        __kmalloc
> > >        fscrypt_setup_filename
> > >        ubifs_tmpfile
> > >        vfs_tmpfile
> > >        path_openat
> > >
> > > Free this memory after it has been copied to the inode.
> > >
> > > Signed-off-by: Mårten Lindahl <marten.lindahl@xxxxxxxx>
> > > ---
> > >   fs/ubifs/dir.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > >
> > > diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
> > > index 0f29cf201136..089ca6910124 100644
> > > --- a/fs/ubifs/dir.c
> > > +++ b/fs/ubifs/dir.c
> > > @@ -491,6 +491,7 @@ static int ubifs_tmpfile(struct user_namespace 
> > > *mnt_userns, struct inode *dir,
> > >           goto out_cancel;
> > >       unlock_2_inodes(dir, inode);
> > >   +    fscrypt_free_filename(&nm);
> > >       ubifs_release_budget(c, &req);
> > >         return finish_open_simple(file, 0);
> >
> > Looks good, just one small nit. I'd prefer to add 
> > fscrypt_free_filename() after ubifs_release_budget() just like 
> > ubifs_create/link does, so that ubifs can get unused budget earlier.
> OK, I will move it after ubifs_release_budget.
> > After looking through the code, I found another place create_whiteout 
> > has the same problem(Imported in 278d9a243635f26c05("ubifs: Rename 
> > whiteout atomically") by me). Would you mind fixing this point just by 
> > removing unused 'nm' in create_whiteout()?
>
> I see what you mean. As I understand it calling fscrypt_setup_filename 
> is not needed in create_whiteout. I would prefer removing those lines in 
> a separate patch since that leak is related to do_rename(). If it's OK 
> with you I can make a patch for that. Would that be OK?

Yes. You may send another patch to fix it. Thanks.