From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0D7F2C433FE for ; Sun, 9 Oct 2022 22:26:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231958AbiJIW0P (ORCPT ); Sun, 9 Oct 2022 18:26:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231881AbiJIWX5 (ORCPT ); Sun, 9 Oct 2022 18:23:57 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC58B3C166; Sun, 9 Oct 2022 15:18:10 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9F307B80DF4; Sun, 9 Oct 2022 22:15:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 83D5AC433D7; Sun, 9 Oct 2022 22:15:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665353726; bh=xHizhrsgBaS+HGjRTXe73ubCJjvU4dsr7/rdK0W9Avo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FP7KdZS3OjunJA9E8Xlj2pFS3r1bulYWIrdtAfNkHejx1bO3rHdT8w/BOea5XRD5O 4ulGA9TBS5oBh7Bt526nIbc0aDJCgCvlhfkhLDPtfG+B8rp4F3Gxbu+gzEYJ3mSYfx npjtZcJZYbQWhnW5gPp3yqpAyf9XEfrlMBYsqwol5Tuv9zSdT8JXh++yGejNbkwSp7 RUkOxiSqOWd5w1GkumfV80l/9JJ5AaVezEmdR2joGkJxoUHKhNh3i2WG0e251uZsWZ RM9yvKuyHrOw5CnLBUR2bMjICDmf/CK2acMUtzL7RJlllNBLbHGUeL/NwaJBdyjsSm a7tQQGHqgEVZA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Quentin Monnet , Daniel Borkmann , Sasha Levin , ast@kernel.org, andrii@kernel.org, bpf@vger.kernel.org Subject: [PATCH AUTOSEL 5.19 05/73] bpftool: Clear errno after libcap's checks Date: Sun, 9 Oct 2022 18:13:43 -0400 Message-Id: <20221009221453.1216158-5-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221009221453.1216158-1-sashal@kernel.org> References: <20221009221453.1216158-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Quentin Monnet [ Upstream commit cea558855c39b7f1f02ff50dcf701ca6596bc964 ] When bpftool is linked against libcap, the library runs a "constructor" function to compute the number of capabilities of the running kernel [0], at the beginning of the execution of the program. As part of this, it performs multiple calls to prctl(). Some of these may fail, and set errno to a non-zero value: # strace -e prctl ./bpftool version prctl(PR_CAPBSET_READ, CAP_MAC_OVERRIDE) = 1 prctl(PR_CAPBSET_READ, 0x30 /* CAP_??? */) = -1 EINVAL (Invalid argument) prctl(PR_CAPBSET_READ, CAP_CHECKPOINT_RESTORE) = 1 prctl(PR_CAPBSET_READ, 0x2c /* CAP_??? */) = -1 EINVAL (Invalid argument) prctl(PR_CAPBSET_READ, 0x2a /* CAP_??? */) = -1 EINVAL (Invalid argument) prctl(PR_CAPBSET_READ, 0x29 /* CAP_??? */) = -1 EINVAL (Invalid argument) ** fprintf added at the top of main(): we have errno == 1 ./bpftool v7.0.0 using libbpf v1.0 features: libbfd, libbpf_strict, skeletons +++ exited with 0 +++ This has been addressed in libcap 2.63 [1], but until this version is available everywhere, we can fix it on bpftool side. Let's clean errno at the beginning of the main() function, to make sure that these checks do not interfere with the batch mode, where we error out if errno is set after a bpftool command. [0] https://git.kernel.org/pub/scm/libs/libcap/libcap.git/tree/libcap/cap_alloc.c?h=libcap-2.65#n20 [1] https://git.kernel.org/pub/scm/libs/libcap/libcap.git/commit/?id=f25a1b7e69f7b33e6afb58b3e38f3450b7d2d9a0 Signed-off-by: Quentin Monnet Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20220815162205.45043-1-quentin@isovalent.com Signed-off-by: Sasha Levin --- tools/bpf/bpftool/main.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c index 9062ef2b8767..0881437587ba 100644 --- a/tools/bpf/bpftool/main.c +++ b/tools/bpf/bpftool/main.c @@ -435,6 +435,16 @@ int main(int argc, char **argv) setlinebuf(stdout); +#ifdef USE_LIBCAP + /* Libcap < 2.63 hooks before main() to compute the number of + * capabilities of the running kernel, and doing so it calls prctl() + * which may fail and set errno to non-zero. + * Let's reset errno to make sure this does not interfere with the + * batch mode. + */ + errno = 0; +#endif + last_do_help = do_help; pretty_output = false; json_output = false; -- 2.35.1