From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH net] bpf: don't zero out the info struct in bpf_obj_get_info_by_fd() Date: Wed, 26 Jul 2017 00:59:49 +0200 Message-ID: <5977CD65.20504@iogearbox.net> References: <20170725221612.6937-1-jakub.kicinski@netronome.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: oss-drivers@netronome.com, alexei.starovoitov@gmail.com, kafai@fb.com To: Jakub Kicinski , netdev@vger.kernel.org Return-path: Received: from www62.your-server.de ([213.133.104.62]:37397 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750919AbdGYXAB (ORCPT ); Tue, 25 Jul 2017 19:00:01 -0400 In-Reply-To: <20170725221612.6937-1-jakub.kicinski@netronome.com> Sender: netdev-owner@vger.kernel.org List-ID: On 07/26/2017 12:16 AM, Jakub Kicinski wrote: > The buffer passed to bpf_obj_get_info_by_fd() should be initialized > to zeros. Kernel will enforce that to guarantee we can safely extend > info structures in the future. > > Making the bpf_obj_get_info_by_fd() call in libbpf perform the zeroing > is problematic, however, since some members of the info structures > may need to be initialized by the callers (for instance pointers > to buffers to which kernel is to dump translated and jited images). > > Remove the zeroing and fix up the in-tree callers before any kernel > has been released with this code. > > As Daniel points out this seems to be the intended operation anyway, > since commit 95b9afd3987f ("bpf: Test for bpf ID") is itself setting > the buffer pointers before calling bpf_obj_get_info_by_fd(). > > Signed-off-by: Jakub Kicinski > --- > I have a small patch to add checking if kernel actually populated > the instruction dumps which I will post after this ends up in net-next. > > tools/lib/bpf/bpf.c | 1 - > tools/testing/selftests/bpf/test_progs.c | 8 ++++++-- > 2 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c > index 412a7c82995a..256f571f2ab5 100644 > --- a/tools/lib/bpf/bpf.c > +++ b/tools/lib/bpf/bpf.c > @@ -314,7 +314,6 @@ int bpf_obj_get_info_by_fd(int prog_fd, void *info, __u32 *info_len) > int err; > > bzero(&attr, sizeof(attr)); > - bzero(info, *info_len); > attr.info.bpf_fd = prog_fd; > attr.info.info_len = *info_len; > attr.info.info = ptr_to_u64(info); > diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c > index 5855cd3d3d45..1f7dd35551b9 100644 > --- a/tools/testing/selftests/bpf/test_progs.c > +++ b/tools/testing/selftests/bpf/test_progs.c > @@ -340,6 +340,7 @@ static void test_bpf_obj_id(void) > > /* Check getting prog info */ > info_len = sizeof(struct bpf_prog_info) * 2; > + bzero(&prog_infos[i], info_len); > prog_infos[i].jited_prog_insns = ptr_to_u64(jited_insns); > prog_infos[i].jited_prog_len = sizeof(jited_insns); > prog_infos[i].xlated_prog_insns = ptr_to_u64(xlated_insns); > @@ -369,6 +370,7 @@ static void test_bpf_obj_id(void) > > /* Check getting map info */ > info_len = sizeof(struct bpf_map_info) * 2; > + bzero(&map_infos[i], info_len); > err = bpf_obj_get_info_by_fd(map_fds[i], &map_infos[i], > &info_len); > if (CHECK(err || > @@ -394,7 +396,7 @@ static void test_bpf_obj_id(void) > nr_id_found = 0; > next_id = 0; > while (!bpf_prog_get_next_id(next_id, &next_id)) { > - struct bpf_prog_info prog_info; > + struct bpf_prog_info prog_info = {}; > int prog_fd; > > info_len = sizeof(prog_info); > @@ -418,6 +420,8 @@ static void test_bpf_obj_id(void) > nr_id_found++; > > err = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &info_len); > + prog_infos[i].jited_prog_insns = 0; > + prog_infos[i].xlated_prog_insns = 0; Can you elaborate why this one above is needed? > CHECK(err || info_len != sizeof(struct bpf_prog_info) || > memcmp(&prog_info, &prog_infos[i], info_len), > "get-prog-info(next_id->fd)", > @@ -436,7 +440,7 @@ static void test_bpf_obj_id(void) > nr_id_found = 0; > next_id = 0; > while (!bpf_map_get_next_id(next_id, &next_id)) { > - struct bpf_map_info map_info; > + struct bpf_map_info map_info = {}; > int map_fd; > > info_len = sizeof(map_info); >