From mboxrd@z Thu Jan 1 00:00:00 1970 From: "bfields@fieldses.org" Subject: Re: [PATCH net-next] SUNRPC: drop pointless static qualifier in xdr_get_next_encode_buffer() Date: Thu, 8 Nov 2018 12:26:33 -0500 Message-ID: <20181108172633.GD4947@fieldses.org> References: <1541642697-33860-1-git-send-email-yuehaibing@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "yuehaibing@huawei.com" , "anna.schumaker@netapp.com" , "davem@davemloft.net" , "jlayton@kernel.org" , "netdev@vger.kernel.org" , "linux-nfs@vger.kernel.org" , "kernel-janitors@vger.kernel.org" To: Trond Myklebust Return-path: Received: from fieldses.org ([173.255.197.46]:38724 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726583AbeKIDDD (ORCPT ); Thu, 8 Nov 2018 22:03:03 -0500 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: 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 > > --- > > 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.