From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by dpdk.org (Postfix) with ESMTP id B81CDC470 for ; Thu, 23 Jun 2016 10:48:26 +0200 (CEST) Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga104.fm.intel.com with ESMTP; 23 Jun 2016 01:48:25 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,509,1459839600"; d="scan'208";a="993498407" Received: from bricha3-mobl3.ger.corp.intel.com ([10.237.220.161]) by fmsmga001.fm.intel.com with SMTP; 23 Jun 2016 01:48:23 -0700 Received: by (sSMTP sendmail emulation); Thu, 23 Jun 2016 09:48:23 +0025 Date: Thu, 23 Jun 2016 09:48:23 +0100 From: Bruce Richardson To: "Jastrzebski, MichalX K" Cc: "Azarewicz, PiotrX T" , "Mrozowicz, SlawomirX" , "dev@dpdk.org" Message-ID: <20160623084822.GA10864@bricha3-MOBL3> References: <1461761554-5900-1-git-send-email-slawomirx.mrozowicz@intel.com> <20160503143404.GA22728@bricha3-MOBL3> <158888A50F43E34AAE179517F56C97455A4043@IRSMSX103.ger.corp.intel.com> <4837007523CC9A4B9414D20C13DE6E64136B3E3D@IRSMSX102.ger.corp.intel.com> <60ABE07DBB3A454EB7FAD707B4BB158213AADDBC@IRSMSX109.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <60ABE07DBB3A454EB7FAD707B4BB158213AADDBC@IRSMSX109.ger.corp.intel.com> Organization: Intel Research and =?iso-8859-1?Q?De=ACvel?= =?iso-8859-1?Q?opment?= Ireland Ltd. User-Agent: Mutt/1.5.23 (2014-03-12) Subject: Re: [dpdk-dev] [PATCH] lpm: unchecked return value X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Jun 2016 08:48:28 -0000 On Thu, Jun 23, 2016 at 09:13:22AM +0100, Jastrzebski, MichalX K wrote: > > -----Original Message----- > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Azarewicz, PiotrX T > > Sent: Thursday, May 12, 2016 1:20 PM > > To: Mrozowicz, SlawomirX ; Richardson, > > Bruce > > Cc: dev@dpdk.org > > Subject: Re: [dpdk-dev] [PATCH] lpm: unchecked return value > > > > Hi, > > > > I handle Coverity defect ID 13201. It is about unchecked return value from > > rte_lpm6_delete() instances in rte_lpm6_add() function. > > Next I found this thread and I see that both defects (ID 13205 and ID 13201) > > may be resolved all together. > > > > > >> Fix issue reported by Coverity. > > > >> > > > >> Coverity ID 13205: Unchecked return value Unchecked return value > > > >> check_return: Calling rte_lpm6_add without checking return value > > > >> Fixes: 5c510e13a9cb ("lpm: add IPv6 support") > > > >> > > > >> Signed-off-by: Slawomir Mrozowicz > > > >> --- > > > >> lib/librte_lpm/rte_lpm6.c | 10 ++++++---- > > > >> 1 file changed, 6 insertions(+), 4 deletions(-) > > > >> > > > >> diff --git a/lib/librte_lpm/rte_lpm6.c b/lib/librte_lpm/rte_lpm6.c > > > >> index ba4353c..f4db3fa 100644 > > > >> --- a/lib/librte_lpm/rte_lpm6.c > > > >> +++ b/lib/librte_lpm/rte_lpm6.c > > > >> @@ -749,6 +749,7 @@ rte_lpm6_delete(struct rte_lpm6 *lpm, uint8_t > > > >> *ip, > > > >uint8_t depth) > > > >> int32_t rule_to_delete_index; > > > >> uint8_t ip_masked[RTE_LPM6_IPV6_ADDR_SIZE]; > > > >> unsigned i; > > > >> + int status = 0; > > > >> > > > >> /* > > > >> * Check input arguments. > > > >> @@ -790,12 +791,13 @@ rte_lpm6_delete(struct rte_lpm6 *lpm, > > uint8_t > > > >*ip, uint8_t depth) > > > >> * Add every rule again (except for the one that was removed from > > > >> * the rules table). > > > >> */ > > > >> - for (i = 0; i < lpm->used_rules; i++) { > > > >> - rte_lpm6_add(lpm, lpm->rules_tbl[i].ip, lpm- > > > >>rules_tbl[i].depth, > > > >> - lpm->rules_tbl[i].next_hop); > > > >> + for (i = 0; i < lpm->used_rules && status >= 0; i++) { > > > >> + status = rte_lpm6_add( > > > >> + lpm, lpm->rules_tbl[i].ip, lpm->rules_tbl[i].depth, > > > >> + lpm->rules_tbl[i].next_hop); > > > >> } > > > >> > > > >> - return 0; > > > >> + return status; > > > >> } > > > > > > > >Hi, > > > > > > > >I'm not sure that this patch is actually necessary, as I'm not sure > > > >that the lpm6_add calls can fail in this instance. Looking through the > > > >code, this function deletes the rule and then clears the actual lpm > > > >lookup tables before re-adding all other routes to it again. The only > > > >error condition that could be returned, that I can see, is -ENOSPC, > > > >which should never occur here since the original rules fitted in the first > > > place. > > > > I agree that -ENOSPC should never occur here. So rte_lpm6_add() instance > > should never fail here. > > > > Next I looked at rte_lpm6_add() and if rte_lpm6_delete() instances in it > > may fail? > > The only suspicious place that I found is place when add every rule again > > but that should work as discussed above. > > > > > > > > > >If it was possible to fail, then I think we would have a worse problem, > > > >in that deleting a single rule has wiped out our lpm table and left it > > > >in an inconsistent state, so the error handling probably needs to be > > better > > > than just quitting. > > > > > > > >Finally, one other thing I spot looking through the code, is that there > > > >seems to be a worrying set of calls between add and delete. If the add > > > >function fails, then it calls delete which in turn will call add again, > > > >etc. etc. This may all work correctly, but it seems fragile and error > > > >prone to me - especially if we allow calls from one to another to fail. > > > > > > > >This looks like it might need some further examination to verify what > > > >the possible failure cases are and what happens in each scenario. > > > > I see no failure scenarios in here. I mean I see no possibility to create test > > that show that add function fail in del and opposite. > > The only scenario what I have in my mind is that someone call add or/and > > del functions on different threads with the same lpm table instance, but > > this is not allowed, cause we know that this functions are not thread safe. > > > > > > > > > >Regards, > > > >/Bruce > > > > > > > > > Hi Bruce, > > > > > > In my opinion the worst-case scenario should be take into account. If > > > function like rte_lpm6_add() returns false then it should be handled. > > > > > > Anyway I agree with you that if the function fail then we have serious > > > problem. > > > I see two problems: > > > 1. Code construction: calls between function rte_lpm6_add() and > > > rte_lpm6_delete(). As you said it should be examined. > > > 2. How we should handle situation if the rules table are not reconstructed > > > after delete operation. > > > > > > I propose to add new issue in ClearQuest to proceed solve the problems > > > because there are extend the original issue (CID 13205 Unchecked return > > > value) from Coverity. > > > > > > Regards, > > > Sławomir > > > > I propose to classify this Coverity issues (ID 13205 and ID 13201) as > > Intentional. > > > > Regards, > > Piotr > > Hi Bruce, > We would like to move forward with theses Coverity defects thus > Please share your opinion about classifying these defects as Intentional? > > Michal >>From previous analysis detailed above, it looks like there is no issue with failing to check the return values here, so I'm ok with this classification. /Bruce