On Thu, Aug 12, 2021 at 4:32 PM J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>
> On Mon, Jun 14, 2021 at 07:14:40PM -0400, bfields wrote:
> > On Wed, Jun 09, 2021 at 05:07:29PM -0400, schumaker.anna@xxxxxxxxx wrote:
> > > From: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
> > >
> > > This seems to happen fairly easily during READ_PLUS testing on NFS v4.2.
> >
> > Yep, I hit a KASAN warning here every time, and this fixes it,
> > thanks.--b.
>
> By the way, config NFS_V4_2_READ_PLUS still says:
>
> This is intended for developers only. The READ_PLUS operation
> has been shown to have issues under specific conditions and
> should not be used in production.
>
> But this warning was the only thing I was seeing. Is there another
> known issue remaining?
I think it was an issue around using lseek to generate the reply. The
file contents could change between each call, leading to inconsistent
results (and a new failing xfstest that previously passed)
Anna
>
> --b.
>
> >
> > > I found that we could end up accessing xdr->buf->pages[pgnr] with a pgnr
> > > greater than the number of pages in the array. So let's just return
> > > early if we're setting base to a point at the end of the page data and
> > > let xdr_set_tail_base() handle setting up the buffer pointers instead.
> > >
> > > Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
> > > ---
> > > net/sunrpc/xdr.c | 7 +++----
> > > 1 file changed, 3 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
> > > index 3964ff74ee51..ca10ba2626f2 100644
> > > --- a/net/sunrpc/xdr.c
> > > +++ b/net/sunrpc/xdr.c
> > > @@ -1230,10 +1230,9 @@ static unsigned int xdr_set_page_base(struct xdr_stream *xdr,
> > > void *kaddr;
> > >
> > > maxlen = xdr->buf->page_len;
> > > - if (base >= maxlen) {
> > > - base = maxlen;
> > > - maxlen = 0;
> > > - } else
> > > + if (base >= maxlen)
> > > + return 0;
> > > + else
> > > maxlen -= base;
> > > if (len > maxlen)
> > > len = maxlen;
> > > --
> > > 2.32.0
