linux-kernel - Re: [PATCH 2/2] hfsplus: add a check for hfs_bnode

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Date:   Thu, 17 Oct 2019 17:52:22 -0300
From:   Ernesto A. Fernández 
        <ernesto.mnd.fernandez@...il.com>
To:     Chuhong Yuan <hslester96@...il.com>
Cc:     linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] hfsplus: add a check for hfs_bnode_find

On Thu, Oct 17, 2019 at 09:30:20AM +0800, Chuhong Yuan wrote:
> On Thu, Oct 17, 2019 at 8:07 AM Ernesto A. Fernández
> <ernesto.mnd.fernandez@...il.com> wrote:
> >
> > Hi,
> >
> > On Wed, Oct 16, 2019 at 08:06:20PM +0800, Chuhong Yuan wrote:
> > > hfs_brec_update_parent misses a check for hfs_bnode_find and may miss
> > > the failure.
> > > Add a check for it like what is done in again.
> > >
> > > Signed-off-by: Chuhong Yuan <hslester96@...il.com>
> > > ---
> > >  fs/hfsplus/brec.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/fs/hfsplus/brec.c b/fs/hfsplus/brec.c
> > > index 1918544a7871..22bada8288c4 100644
> > > --- a/fs/hfsplus/brec.c
> > > +++ b/fs/hfsplus/brec.c
> > > @@ -434,6 +434,8 @@ static int hfs_brec_update_parent(struct hfs_find_data *fd)
> > >                       new_node->parent = tree->root;
> > >               }
> > >               fd->bnode = hfs_bnode_find(tree, new_node->parent);
> > > +             if (IS_ERR(fd->bnode))
> > > +                     return PTR_ERR(fd->bnode);
> >
> > You shouldn't just return here, you still hold a reference to new_node.
> > The call to hfs_bnode_find() after the again label seems to be making a
> > similar mistake.
> >
> > I don't think either one can actually fail though, because the parent
> > nodes have all been read and hashed before, haven't they?
> >
> 
> I find that after hfs_bnode_findhash in hfs_bnode_find, there is a test for
> HFS_BNODE_ERROR and may return an error. I'm not sure whether it
> can happen here.

That would require a race between hfs_bnode_find() and hfs_bnode_create(),
but the node has already been created.

> 
> > >               /* create index key and entry */
> > >               hfs_bnode_read_key(new_node, fd->search_key, 14);
> > >               cnid = cpu_to_be32(new_node->this);
> > > --
> > > 2.20.1
> > >