From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH v1 net-next] net: filter: fix length calculation in BPF testsuite Date: Thu, 29 May 2014 22:41:28 +0200 Message-ID: <53879B78.5050106@redhat.com> References: <1401391757-27620-1-git-send-email-chema@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: David Miller , Eric Dumazet , Alexei Starovoitov , netdev@vger.kernel.org To: Chema Gonzalez Return-path: Received: from mx1.redhat.com ([209.132.183.28]:58036 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754147AbaE2Uln (ORCPT ); Thu, 29 May 2014 16:41:43 -0400 In-Reply-To: <1401391757-27620-1-git-send-email-chema@google.com> Sender: netdev-owner@vger.kernel.org List-ID: On 05/29/2014 09:29 PM, Chema Gonzalez wrote: > The current probe_filter_length() (the function that calculates the > length of a test BPF filter) behavior is to declare the end of the > filter as soon as it finds {0, *, *, 0}. This is actually a valid > insn ("ld #0"), so any filter with includes "BPF_STMT(BPF_LD | BPF_IMM, 0)" > fails (its length is cut short). > > We are changing probe_filter_length() so as to start from the end, and > declare the end of the filter as the first instruction which is not > {0, *, *, 0}. This solution produces a simpler patch than the > alternative of using an explicit end-of-filter mark. It is technically > incorrect if your filter ends up with "ld #0", but that should not > happen anyway. > > We also add a new test (LD_IMM_0) that includes ld #0 (does not work > without this patch). > > Signed-off-by: Chema Gonzalez Looks good to me, thanks a lot Chema! Acked-by: Daniel Borkmann > + for (len = MAX_INSNS-1; len > 0; --len) > + if (fp[len].code != 0 || fp[len].k != 0) > + break; > > - return len; > + return len+1; Nit: would be great to have a whitespace between MAX_INSNS-1 and len+1 but that shouldn't matter that much, perhaps.