From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Metcalf Subject: Re: [PATCH 0/3] add new strscpy() API for string copy Date: Fri, 15 May 2015 11:15:27 -0400 Message-ID: <55560D8F.60704@ezchip.com> References: <1430409677-13284-1-git-send-email-cmetcalf@ezchip.com> <1431645018.2981.3.camel@ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-am1on0067.outbound.protection.outlook.com ([157.56.112.67]:31264 "EHLO emea01-am1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754101AbbEOPPn (ORCPT ); Fri, 15 May 2015 11:15:43 -0400 In-Reply-To: <1431645018.2981.3.camel@ellerman.id.au> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Michael Ellerman Cc: Linus Torvalds , Al Viro , Fabian Frederick , Randy Dunlap , Rickard Strandqvist , gregkh@linuxfoundation.org, Peter Zijlstra , "David S. Miller" , Frederic Weisbecker , Andrew Morton , Sam Ravnborg , Stephen Rothwell , Theodore Ts'o , Grant Likely , Linux Kernel Mailing List , linux-arch@vger.kernel.org On 05/14/2015 07:10 PM, Michael Ellerman wrote: > On Thu, 2015-04-30 at 12:01 -0400, Chris Metcalf wrote: >> This patch series addresses limitations in strncpy() and strlcpy(); >> both the old APIs are unpleasant, as Linus nicely summarized here >> a couple of days ago: >> >> https://lkml.org/lkml/2015/4/28/570 >> >> and of course as other folks (Greg K-H and Linus again) said last year: >> >> https://plus.google.com/+gregkroahhartman/posts/1amLbuhWbh5 >> >> The proposed new API (strscpy(), for "s"afe string copy) has an >> easy-to-use API for detecting buffer overflow, avoids unsafe truncation >> by default, and isn't subject to thread-safety attacks like the current >> strlcpy implementation. See patch 2/3 for more on why strscpy() is a >> good thing. > +1 on the concept. Thanks. >> To make strscpy() work more efficiently I did the minimum tweaking >> necessary to allow to work on all architectures, >> though of course individual maintainers can still make their versions >> more efficient as needed. >> >> It's likely not necessary for per-architecture implementations of >> strscpy() to be written, but I stuck with the standard __HAVE_ARCH_XXX >> model just for consistency with the rest of . >> >> I tested the implementation with a simple user-space harness, so I >> believe it is correct for the corner cases I could think of. In >> particular I pairwise-tested all the unaligned values of source and >> dest, and tested the restriction on src page-crossing at all >> unaligned offsets approaching the page boundary. > Can you please put that in tools/testing/selftests and merge it as part of the > series? That way I can run the tests and be confident it works on powerpc. Unfortunately, the strscpy patch series only changes the one previous user of the API, which is a tile-architecture-only driver piece, not particularly useful for anyone else for testing. The testing I did pulled strscpy() and word-at-a-time out into a separate, standalone userspace implementation, and tested it there, rather than doing tests through the syscall API like tools/testing/selftests. So I don't really see a way of committing my test framework, other than as a real Kconfig-enabled boot-time self-test or some such; I can certainly do that but I don't know how excited people are to have that additional level of source-code and Kconfig bloat. -- Chris Metcalf, EZChip Semiconductor http://www.ezchip.com