From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH bpf-next] bpf: correct slot_type marking logic to allow more stack slot sharing Date: Tue, 18 Dec 2018 23:28:34 +0100 Message-ID: <9c1d60cd-281b-1223-a7dd-aff142410fd0@iogearbox.net> References: <1544862880-23291-1-git-send-email-jiong.wang@netronome.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, oss-drivers@netronome.com To: Jiong Wang , ast@kernel.org Return-path: Received: from www62.your-server.de ([213.133.104.62]:36698 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726595AbeLRW2h (ORCPT ); Tue, 18 Dec 2018 17:28:37 -0500 In-Reply-To: <1544862880-23291-1-git-send-email-jiong.wang@netronome.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 12/15/2018 09:34 AM, Jiong Wang wrote: > Verifier is supposed to support sharing stack slot allocated to ptr with > SCALAR_VALUE for privileged program. However this doesn't happen for some > cases. > > The reason is verifier is not clearing slot_type STACK_SPILL for all bytes, > it only clears part of them, while verifier is using: > > slot_type[0] == STACK_SPILL > > as a convention to check one slot is ptr type. > > So, the consequence of partial clearing slot_type is verifier could treat a > partially overridden ptr slot, which should now be a SCALAR_VALUE slot, > still as ptr slot, and rejects some valid programs. > > Before this patch, test_xdp_noinline.o under bpf selftests, bpf_lxc.o and > bpf_netdev.o under Cilium bpf repo, when built with -mattr=+alu32 are > rejected due to this issue. After this patch, they all accepted. > > There is no processed insn number change before and after this patch on > Cilium bpf programs. > > Reviewed-by: Jakub Kicinski > Signed-off-by: Jiong Wang Reviewed-by: Daniel Borkmann