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SubjectRe: [PATCH 2/3] NILFS2: support NFSv2 export
On Mon, 11 May 2015 01:31:43 +0900 (JST) Ryusuke Konishi
<konishi.ryusuke@lab.ntt.co.jp> wrote:

> On Fri, 08 May 2015 10:16:23 +1000, NeilBrown <neilb@suse.de> wrote:
> > The "fh_len" passed to ->fh_to_* is not guaranteed to be that same as
> > that returned by encode_fh - it may be larger.
> >
> > With NFSv2, the filehandle is fixed length, so it may appear longer
> > than expected and be zero-padded.
> >
> > So we must test that fh_len is at least some value, not exactly equal
> > to it.
> >
> > Signed-off-by: NeilBrown <neilb@suse.de>
> > ---
> > fs/nilfs2/namei.c | 6 +++---
> > 1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/nilfs2/namei.c b/fs/nilfs2/namei.c
> > index 22180836ec22..b65fb79d16fd 100644
> > --- a/fs/nilfs2/namei.c
> > +++ b/fs/nilfs2/namei.c
> > @@ -496,8 +496,8 @@ static struct dentry *nilfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
> > {
> > struct nilfs_fid *fid = (struct nilfs_fid *)fh;
> >
> > - if ((fh_len != NILFS_FID_SIZE_NON_CONNECTABLE &&
> > - fh_len != NILFS_FID_SIZE_CONNECTABLE) ||
>
> > + if ((fh_len < NILFS_FID_SIZE_NON_CONNECTABLE &&
> > + fh_len < NILFS_FID_SIZE_CONNECTABLE) ||
> > (fh_type != FILEID_NILFS_WITH_PARENT &&
> > fh_type != FILEID_NILFS_WITHOUT_PARENT))
> > return NULL;
>
> A bit weird. "fh_len < NILFS_FID_SIZE_CONNECTABLE" implies "fh_len <
> NILFS_FID_SIZE_NON_CONNECTABLE".
>
> How about the following fix ?
>
> if ((fh_type != FILEID_NILFS_WITH_PARENT ||
> fh_len < NILFS_FID_SIZE_CONNECTABLE) &&
> (fh_type != FILEID_NILFS_WITHOUT_PARENT ||
> fh_len < NILFS_FID_SIZE_NON_CONNECTABLE))
> return NULL;
>

Yes, weird. The code only uses the early parts of the filehandle, so we
only need to complain if the fh_len is less than FILEID_NILFS_WITHOUT_PARENT.

So I'd prefer:

@@ -496,8 +496,7 @@ static struct dentry *nilfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
{
struct nilfs_fid *fid = (struct nilfs_fid *)fh;

- if ((fh_len != NILFS_FID_SIZE_NON_CONNECTABLE &&
- fh_len != NILFS_FID_SIZE_CONNECTABLE) ||
+ if (fh_len < NILFS_FID_SIZE_NON_CONNECTABLE ||
(fh_type != FILEID_NILFS_WITH_PARENT &&
fh_type != FILEID_NILFS_WITHOUT_PARENT))
return NULL;


Would you be OK with that? If so I'll resend.

Thanks,
NeilBrown
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