linux-kernel - Re: [PATCH] jffs2: fix invocations of dbg_xattr() for dead jffs2_xattr

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Date:   Thu, 13 Dec 2018 22:53:02 +0100
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     boris.brezillon@...tlin.com
Cc:     houtao1@...wei.com, linux-mtd@...ts.infradead.org,
        David Woodhouse <dwmw2@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] jffs2: fix invocations of dbg_xattr() for dead jffs2_xattr_ref

On Sun, Dec 9, 2018 at 7:52 AM Boris Brezillon
<boris.brezillon@...tlin.com> wrote:
>
> On Sat, 20 Oct 2018 19:07:53 +0800
> Hou Tao <houtao1@...wei.com> wrote:
>
> > When jffs2_xattr_ref is dead, xref->ic or xref->xd will be invalid
> > because these fields will be reused as xref->ino or xref->xid,
> > so access xref->ic->ino or xref->xd->xid will lead to Oops.
> >
> > Fix the problem by checking whether or not it is a dead xref.
> >
> > Signed-off-by: Hou Tao <houtao1@...wei.com>
> > ---
> >  fs/jffs2/xattr.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/jffs2/xattr.c b/fs/jffs2/xattr.c
> > index 3d40fe02b003..0c4c7891556d 100644
> > --- a/fs/jffs2/xattr.c
> > +++ b/fs/jffs2/xattr.c
> > @@ -550,7 +550,8 @@ static int save_xattr_ref(struct jffs2_sb_info *c, struct jffs2_xattr_ref *ref)
> >       ref->xseqno = xseqno;
> >       jffs2_add_physical_node_ref(c, phys_ofs | REF_PRISTINE, PAD(sizeof(rr)), (void *)ref);
> >
> > -     dbg_xattr("success on saving xref (ino=%u, xid=%u)\n", ref->ic->ino, ref->xd->xid);
> > +     dbg_xattr("success on saving xref (ino=%u, xid=%u)\n",
> > +                     je32_to_cpu(rr.ino), je32_to_cpu(rr.xid));
>
> Nit: align the second line on the open parens (same applies to the
> other chunk).
>
> Sorry, I can't comment on the actual change. I'll let Richard look
> at it.
>
> >
> >       return 0;
> >  }
> > @@ -1329,7 +1330,11 @@ int jffs2_garbage_collect_xattr_ref(struct jffs2_sb_info *c, struct jffs2_xattr_
> >       rc = save_xattr_ref(c, ref);
> >       if (!rc)
> >               dbg_xattr("xref (ino=%u, xid=%u) GC'ed from %#08x to %08x\n",
> > -                       ref->ic->ino, ref->xd->xid, old_ofs, ref_offset(ref->node));
> > +                             is_xattr_ref_dead(ref) ?
> > +                                     ref->ino : ref->ic->ino,
> > +                             is_xattr_ref_dead(ref) ?
> > +                                     ref->xid : ref->xd->xid,
> > +                             old_ofs, ref_offset(ref->node));
> >   out:
> >       if (!rc)
> >               jffs2_mark_node_obsolete(c, raw);
>

Since is_xattr_ref_dead() is cheap, can you please add two macros.
Something like:
static inline uint32_t xattr_ref_ino(struct jffs2_xattr_ref *ref) {
 if (is_xattr_ref_dead(ref))
  return ref>ino;
 else
  return ref->ic->ino;
}

Same for xid.
-- 
Thanks,
//richard