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 A66A4C43219 for ; Sun, 9 Oct 2022 22:50:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233484AbiJIWuW (ORCPT ); Sun, 9 Oct 2022 18:50:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58258 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233493AbiJIWtN (ORCPT ); Sun, 9 Oct 2022 18:49:13 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B5FAB40E0E; Sun, 9 Oct 2022 15:25:39 -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 93D65B80DE2; Sun, 9 Oct 2022 22:23:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 965C0C4347C; Sun, 9 Oct 2022 22:23:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1665354193; bh=ZrB31+NJNwQic7KGl2gvkCCBKpq/6mExqiYHUP8iVO4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bOj66cVkjcr55G5TanPEetacZ/u5OUfCclteenjBq4UhqY1oCeKcKYFd0jIhEZtEL Pv+NHFejPOQWcMenJXQPMGruRqw5DOAhXe8SO41+0TVuanWyW/RSdjcTyvLX50dVWI oQUThPQxdbD7jexLxgIuiZttySepp1bX21Zd29tJl/7c92wGfpq5slA4DoCvSr5Gsm vNgKB4sjb9TZTLvCSVu7DDTXWusnX1e2XCLnuHiBoaZWsfeRWYjbR2y9zAiyOxvgbT mn6H9io1iHof2VOf0qPngjdiAa2LjP4w+uF+R6vYFfORtgBJWEtI1Rg/vJfy3SvqtZ BPjZKFYtz+Vqw== 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 5.4 03/29] bpftool: Clear errno after libcap's checks Date: Sun, 9 Oct 2022 18:22:38 -0400 Message-Id: <20221009222304.1218873-3-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20221009222304.1218873-1-sashal@kernel.org> References: <20221009222304.1218873-1-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: bpf@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 4b03983acbef..35984bd354cb 100644 --- a/tools/bpf/bpftool/main.c +++ b/tools/bpf/bpftool/main.c @@ -364,6 +364,16 @@ 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