From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chema Gonzalez Subject: [PATCH v2 net-next] net: filter: fix length calculation in BPF testsuite Date: Fri, 30 May 2014 10:15:12 -0700 Message-ID: <1401470112-3933-1-git-send-email-chema@google.com> References: <53879B78.5050106@redhat.com> Cc: netdev@vger.kernel.org, Chema Gonzalez To: David Miller , Eric Dumazet , Daniel Borkmann , Alexei Starovoitov Return-path: Received: from mail-yh0-f74.google.com ([209.85.213.74]:48096 "EHLO mail-yh0-f74.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965068AbaE3RPO (ORCPT ); Fri, 30 May 2014 13:15:14 -0400 Received: by mail-yh0-f74.google.com with SMTP id 29so461840yhl.1 for ; Fri, 30 May 2014 10:15:13 -0700 (PDT) In-Reply-To: <53879B78.5050106@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: 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 --- lib/test_bpf.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/lib/test_bpf.c b/lib/test_bpf.c index af677cb..e60f766 100644 --- a/lib/test_bpf.c +++ b/lib/test_bpf.c @@ -158,6 +158,18 @@ static struct bpf_test tests[] = { { { 0, 0x800000ff }, { 1, 0x800000ff } }, }, { + "LD_IMM_0", + .u.insns = { + BPF_STMT(BPF_LD | BPF_IMM, 0), /* ld #0 */ + BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0, 1, 0), + BPF_STMT(BPF_RET | BPF_K, 0), + BPF_STMT(BPF_RET | BPF_K, 1), + }, + CLASSIC, + { }, + { { 1, 1 } }, + }, + { "LD_IND", .u.insns = { BPF_STMT(BPF_LDX | BPF_LEN, 0), @@ -1542,12 +1554,11 @@ static int probe_filter_length(struct sock_filter *fp) { int len = 0; - while (fp->code != 0 || fp->k != 0) { - fp++; - len++; - } + for (len = MAX_INSNS - 1; len > 0; --len) + if (fp[len].code != 0 || fp[len].k != 0) + break; - return len; + return len + 1; } static struct sk_filter *generate_filter(int which, int *err) -- 1.9.1.423.g4596e3a