On Thu, Nov 08, 2018 at 03:13:25AM +0000, Trond Myklebust wrote:
> On Thu, 2018-11-08 at 02:04 +0000, YueHaibing wrote:
> > There is no need to have the '__be32 *p' variable static since new
> > value
> > always be assigned before use it.
Applying for 4.20 and stable, thanks!
> >
> > Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
> > ---
> > net/sunrpc/xdr.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
> > index 2bbb8d3..d80b156 100644
> > --- a/net/sunrpc/xdr.c
> > +++ b/net/sunrpc/xdr.c
> > @@ -546,7 +546,7 @@ void xdr_commit_encode(struct xdr_stream *xdr)
> > static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
> > size_t nbytes)
> > {
> > - static __be32 *p;
> > + __be32 *p;
> > int space_left;
> > int frag1bytes, frag2bytes;
> >
>
> Ouch, that's a really nasty bug that could definitely cause corruption
> if you have 2 threads simultaneously calling this function! This really
> deserves to be a stable patch.
Agreed. Looks like I introduced that in 3.16, over 5 years ago, so I'm
a little surprised not to have seen a bug report that this would
explain. Maybe it's just that the critical section is only a few lines
of arithemtic at the end of the function. Also it only gets called when
an xdr reply other than a read reaches the end of a page. So you'd need
a lot of concurrent READDIRs of large directories or something. Still,
I'd think it would be possible.....
> Thank you, YueHaibing!
>
> Bruce, do you want to shepherd this one in?
Yes, I've got 3 bugfixes queued up now, I should send them along later
today or tomorrow.
--b.
