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

[Mårten Lindahl]

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?

Kind regards

Mårten

> > ---
> > base-commit: c9c3395d5e3dcc6daee66c6908354d47bf98cb0c
> > change-id: 20230329-memleak-fix-87a01daf469e
> >
> > Best regards,