From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57659C55179 for ; Fri, 6 Nov 2020 21:00:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A09E720B1F for ; Fri, 6 Nov 2020 21:00:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fieldses.org header.i=@fieldses.org header.b="oMy1IPfl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728493AbgKFVAA (ORCPT ); Fri, 6 Nov 2020 16:00:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727129AbgKFVAA (ORCPT ); Fri, 6 Nov 2020 16:00:00 -0500 Received: from fieldses.org (fieldses.org [IPv6:2600:3c00:e000:2f7::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 89580C0613CF; Fri, 6 Nov 2020 13:00:00 -0800 (PST) Received: by fieldses.org (Postfix, from userid 2815) id 2387535D4; Fri, 6 Nov 2020 15:59:59 -0500 (EST) DKIM-Filter: OpenDKIM Filter v2.11.0 fieldses.org 2387535D4 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fieldses.org; s=default; t=1604696399; bh=uERgbadAtWsWY3k626vTNOyPzlTv6M6dkoAgVGh6RxY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oMy1IPflCw126dEz+g6MhHHCQeONZRy1e/GnSU9qeG0CnG3J+BvTQnDx5A1+saMxt lm5DnUGyOYKTV89h1giq2lp36vMR79RadgJiUIwlz5vHE1zc34vNjd+joM519jqlOa OnqFU6y67HGcgQ04Y2bIkqmh8CvRyVMbVsdbI598= Date: Fri, 6 Nov 2020 15:59:59 -0500 From: "J. Bruce Fields" To: Dan Carpenter Cc: Trond Myklebust , Artur Molchanov , Anna Schumaker , Chuck Lever , Jakub Kicinski , linux-nfs@vger.kernel.org, kernel-janitors@vger.kernel.org, Colin King Subject: Re: [PATCH] net/sunrpc: clean up error checking in proc_do_xprt() Message-ID: <20201106205959.GB26028@fieldses.org> References: <031F93AC-744F-4E02-9948-1C1F5939714B@gmail.com> <20201027141758.GA3488087@mwanda> <20201106203316.GA26028@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201106203316.GA26028@fieldses.org> User-Agent: Mutt/1.5.21 (2010-09-15) Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Fri, Nov 06, 2020 at 03:33:16PM -0500, J. Bruce Fields wrote: > On Tue, Oct 27, 2020 at 05:17:58PM +0300, Dan Carpenter wrote: > > There are three changes but none of them should affect run time: > > > > 1) You can't write to this file because the permissions are 0444. But > > it sort of looked like you could do a write and it would result in > > a read. Then it looked like proc_sys_call_handler() just ignored > > it. Which is confusing. It's more clear if the "write" just > > returns zero. > > 2) The "lenp" pointer is never NULL so that check can be removed. > > 3) In the original code, the "if (*lenp < 0)" check didn't work because > > "*lenp" is unsigned. Fortunately, the memory_read_from_buffer() > > call will never fail in this context so it doesn't affect runtime. > > > > Signed-off-by: Dan Carpenter > > --- > > net/sunrpc/sysctl.c | 18 +++++++++--------- > > 1 file changed, 9 insertions(+), 9 deletions(-) > > > > diff --git a/net/sunrpc/sysctl.c b/net/sunrpc/sysctl.c > > index a18b36b5422d..04526bab4a06 100644 > > --- a/net/sunrpc/sysctl.c > > +++ b/net/sunrpc/sysctl.c > > @@ -63,19 +63,19 @@ static int proc_do_xprt(struct ctl_table *table, int write, > > void *buffer, size_t *lenp, loff_t *ppos) > > { > > char tmpbuf[256]; > > - size_t len; > > + ssize_t len; > > > > - if ((*ppos && !write) || !*lenp) { > > - *lenp = 0; > > + *lenp = 0; > > + > > + if (write || *ppos) > > return 0; > > - } > > + > > len = svc_print_xprts(tmpbuf, sizeof(tmpbuf)); > > - *lenp = memory_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len); > > + len = memory_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len); > > Except now we're passing *lenp = 0, that can't be right. > > Though I actually kind of prefer this to Colin King's patch which just > casts (*lenp) in the comparison below. So, maybe just leave all the ugly *lenp = 0's and otherwise keep your version: commit d435c05ab019 Author: Dan Carpenter Date: Fri Nov 6 15:39:50 2020 -0500 net/sunrpc: return 0 on attempt to write to "transports" You can't write to this file because the permissions are 0444. But it sort of looked like you could do a write and it would result in a read. Then it looked like proc_sys_call_handler() just ignored it. Which is confusing. It's more clear if the "write" just returns zero. Also, the "lenp" pointer is never NULL so that check can be removed. Signed-off-by: Dan Carpenter Signed-off-by: J. Bruce Fields diff --git a/net/sunrpc/sysctl.c b/net/sunrpc/sysctl.c index a18b36b5422d..5c9f5bca4d99 100644 --- a/net/sunrpc/sysctl.c +++ b/net/sunrpc/sysctl.c @@ -65,7 +65,7 @@ static int proc_do_xprt(struct ctl_table *table, int write, char tmpbuf[256]; size_t len; - if ((*ppos && !write) || !*lenp) { + if (write || *ppos) { *lenp = 0; return 0; } commit bfb5aa1685d5 Author: Dan Carpenter Date: Fri Nov 6 15:50:39 2020 -0500 net/sunrpc: fix useless comparison in proc_do_xprt() In the original code, the "if (*lenp < 0)" check didn't work because "*lenp" is unsigned. Fortunately, the memory_read_from_buffer() call will never fail in this context so it doesn't affect runtime. Signed-off-by: J. Bruce Fields diff --git a/net/sunrpc/sysctl.c b/net/sunrpc/sysctl.c index 5c9f5bca4d99..3aad6ef18504 100644 --- a/net/sunrpc/sysctl.c +++ b/net/sunrpc/sysctl.c @@ -63,19 +63,20 @@ static int proc_do_xprt(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { char tmpbuf[256]; - size_t len; + ssize_t len; if (write || *ppos) { *lenp = 0; return 0; } len = svc_print_xprts(tmpbuf, sizeof(tmpbuf)); - *lenp = memory_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len); + len = memory_read_from_buffer(buffer, *lenp, ppos, tmpbuf, len); - if (*lenp < 0) { + if (len < 0) { *lenp = 0; return -EINVAL; } + *lenp = len; return 0; }