linux-kernel - Re: [PATCH] NFSv4: Fix a memory leak bug

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Date:   Tue, 20 Aug 2019 14:53:47 -0400
From:   Wenwen Wang <wenwen@...uga.edu>
To:     "Schumaker, Anna" <Anna.Schumaker@...app.com>
Cc:     "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "trond.myklebust@...merspace.com" <trond.myklebust@...merspace.com>,
        Wenwen Wang <wenwen@...uga.edu>
Subject: Re: [PATCH] NFSv4: Fix a memory leak bug

On Tue, Aug 20, 2019 at 9:41 AM Schumaker, Anna
<Anna.Schumaker@...app.com> wrote:
>
> Hi Wenwen,
>
> On Tue, 2019-08-20 at 02:54 -0500, Wenwen Wang wrote:
> > In nfs4_try_migration(), if nfs4_begin_drain_session() fails, the
> > previously allocated 'page' and 'locations' are not deallocated,
> > leading to
> > memory leaks. To fix this issue, free 'page' and 'locations' before
> > returning the error.
> >
> > Signed-off-by: Wenwen Wang <wenwen@...uga.edu>
> > ---
> >  fs/nfs/nfs4state.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> > index cad4e06..37823dc 100644
> > --- a/fs/nfs/nfs4state.c
> > +++ b/fs/nfs/nfs4state.c
> > @@ -2095,8 +2095,12 @@ static int nfs4_try_migration(struct
> > nfs_server *server, const struct cred *cred
> >         }
> >
> >         status = nfs4_begin_drain_session(clp);
> > -       if (status != 0)
> > +       if (status != 0) {
> > +               if (page != NULL)
> > +                       __free_page(page);
> > +               kfree(locations);
> >                 return status;
>
> Thanks for the suggestion! I think a better option would be to switch
> the "return status" into a "goto out" so we can keep all our cleanup
> code in a single place in case we ever need to change it in the future.
>
> What do you think?

Thanks for your comments! I will rework the patch.

Wenwen

> Anna
>
> > +       }
> >
> >         status = nfs4_replace_transport(server, locations);
> >         if (status != 0) {
> > --
> > 2.7.4
> >