From patchwork Fri Jan 20 10:25:11 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Giuseppe Scrivano X-Patchwork-Id: 46283 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:adf:eb09:0:0:0:0:0 with SMTP id s9csp121160wrn; Fri, 20 Jan 2023 02:30:30 -0800 (PST) X-Google-Smtp-Source: AMrXdXt4wH3UYASjiblcuxhtnUsde2iPhZZ47gp2x/D0Pwx14IjiA4kvdqgdA6oYUXAQCmugBqAs X-Received: by 2002:a17:902:e548:b0:194:687c:e883 with SMTP id n8-20020a170902e54800b00194687ce883mr20538449plf.37.1674210630059; Fri, 20 Jan 2023 02:30:30 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1674210630; cv=none; d=google.com; s=arc-20160816; b=EwV3WFoc5SC7NMbjPnBOd9US0b/xjCgMP0e+hSTw64mQDnCOfYTqoO73XqU0nuX6Cy hz5Et7C6Tys6lmBeqdkeH5x7z5SKGOurm+LmGOLPSL6fmFHyz/w7Qn8u3u1k1Nk1tVHv RyLSdA+WJgbQ9bfIUjvUlVCTJQtcu4B6E3K6v53NQeUNIq23Q60Zsa52+pIc8t66QiZh dn3KQIMnzS4RWiW8vpvZMde28/+0pOOcHOT5hOiumGhRrQ6ZT/WkOUCkD6BHgx8hnR2x 0BkBDCi38DTvLbNyuz3i29BWD/klzHn5lUJGODHCF2lYtNyz6Xbp5z1pQOVmmzZ8kU7X 5kvA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :message-id:date:subject:cc:to:from:dkim-signature; bh=ieCymmvmHcLwxBMNWiBKMIP9Q3Vx9XZSJMoHLCt0yd4=; b=yd0qh5fh3RpK+pbFiuZWW9w3kF24f6AD3/olc62KpdcWK2d3hnToltl0KJFq8CYGmg XVUYZ1pDIAhJ9tc2fxJzudU2cAnvZ0QFUxgSQWDvWRi2zS30HbDcXdINQLAxWGZJnn+c j6/tjfK64MdhFJpQQGSd3ecoZIOUgmrQ3cEbBLYkcJlzo1l0trzsEVvIdYpXA8xqFig/ f686uGM5mzRf/nB8kSXjCC078xeAM+DW1gEjJfbiWtfia99Czq1Zu6r/YGA0ZWwvQ0IY zFibq9Bji3R0F5gpQzwHsD9SR20FEOZLhAXgpczfU+W9sE0Vlxay8sMVUAqZAqRPuG1P gkvw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=YxFqShtE; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id b5-20020a170902e94500b001787f1922a7si23219408pll.19.2023.01.20.02.30.17; Fri, 20 Jan 2023 02:30:30 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=YxFqShtE; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229749AbjATK01 (ORCPT + 99 others); Fri, 20 Jan 2023 05:26:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229897AbjATK0U (ORCPT ); Fri, 20 Jan 2023 05:26:20 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3EE28B76A for ; Fri, 20 Jan 2023 02:25:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674210337; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=ieCymmvmHcLwxBMNWiBKMIP9Q3Vx9XZSJMoHLCt0yd4=; b=YxFqShtEbNs/Br8Gk3hVeYdkcENuR4IjEXcTk2DLTZyfNSkNKRm6Tqk+nlcACgiLrVPx1r LFyDULaWjxuLB0Q1Vb8xT2r8MbBbfy/N4dwNOe+lPjsRtxYGLwVtzSI2N5WFGS6WN2B7ju EP3T6vAOUoz/o9daejmRNvRwu5At5nE= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-448-V7OXi7UvNzqjtAFUhAJTDw-1; Fri, 20 Jan 2023 05:25:34 -0500 X-MC-Unique: V7OXi7UvNzqjtAFUhAJTDw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 34B2718E0924; Fri, 20 Jan 2023 10:25:34 +0000 (UTC) Received: from lithium.redhat.com (unknown [10.39.194.249]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1E98F53AA; Fri, 20 Jan 2023 10:25:31 +0000 (UTC) From: Giuseppe Scrivano To: linux-kernel@vger.kernel.org Cc: keescook@chromium.org, bristot@redhat.com, ebiederm@xmission.com, brauner@kernel.org, cyphar@cyphar.com, viro@zeniv.linux.org.uk, alexl@redhat.com, peterz@infradead.org, bmasney@redhat.com, gscrivan@redhat.com Subject: [PATCH v3 1/2] exec: add PR_HIDE_SELF_EXE prctl Date: Fri, 20 Jan 2023 11:25:11 +0100 Message-Id: <20230120102512.3195094-1-gscrivan@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1755537085425460256?= X-GMAIL-MSGID: =?utf-8?q?1755537085425460256?= This patch adds a new prctl called PR_HIDE_SELF_EXE which allows processes to hide their own /proc/*/exe file. When this prctl is used, every access to /proc/*/exe for the calling process will fail with ENOENT. This is useful for preventing issues like CVE-2019-5736, where an attacker can gain host root access by overwriting the binary in OCI runtimes through file-descriptor mishandling in containers. The current fix for CVE-2019-5736 is to create a read-only copy or a bind-mount of the current executable, and then re-exec the current process. With the new prctl, the read-only copy or bind-mount copy is not needed anymore. While map_files/ also might contain symlinks to files in host, proc_map_files_get_link() permissions checks are already sufficient. Signed-off-by: Giuseppe Scrivano Reviewed-by: Kees Cook --- v2: https://lkml.org/lkml/2023/1/19/849 Differences from v2: - fixed the test to check PR_SET_HIDE_SELF_EXE after fork v1: https://lkml.org/lkml/2023/1/4/334 Differences from v1: - amended more information in the commit message wrt map_files not requiring the same protection. - changed the test to verify PR_HIDE_SELF_EXE cannot be unset after a fork. fs/exec.c | 1 + fs/proc/base.c | 8 +++++--- include/linux/sched.h | 5 +++++ include/uapi/linux/prctl.h | 3 +++ kernel/sys.c | 9 +++++++++ tools/include/uapi/linux/prctl.h | 3 +++ 6 files changed, 26 insertions(+), 3 deletions(-) diff --git a/fs/exec.c b/fs/exec.c index ab913243a367..5a5dd964c3a3 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1855,6 +1855,7 @@ static int bprm_execve(struct linux_binprm *bprm, /* execve succeeded */ current->fs->in_exec = 0; current->in_execve = 0; + task_clear_hide_self_exe(current); rseq_execve(current); acct_update_integrals(current); task_numa_free(current, false); diff --git a/fs/proc/base.c b/fs/proc/base.c index 9e479d7d202b..959968e2da0d 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1723,19 +1723,21 @@ static int proc_exe_link(struct dentry *dentry, struct path *exe_path) { struct task_struct *task; struct file *exe_file; + long hide_self_exe; task = get_proc_task(d_inode(dentry)); if (!task) return -ENOENT; exe_file = get_task_exe_file(task); + hide_self_exe = task_hide_self_exe(task); put_task_struct(task); - if (exe_file) { + if (exe_file && !hide_self_exe) { *exe_path = exe_file->f_path; path_get(&exe_file->f_path); fput(exe_file); return 0; - } else - return -ENOENT; + } + return -ENOENT; } static const char *proc_pid_get_link(struct dentry *dentry, diff --git a/include/linux/sched.h b/include/linux/sched.h index 853d08f7562b..8db32d5fc285 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1790,6 +1790,7 @@ static __always_inline bool is_percpu_thread(void) #define PFA_SPEC_IB_DISABLE 5 /* Indirect branch speculation restricted */ #define PFA_SPEC_IB_FORCE_DISABLE 6 /* Indirect branch speculation permanently restricted */ #define PFA_SPEC_SSB_NOEXEC 7 /* Speculative Store Bypass clear on execve() */ +#define PFA_HIDE_SELF_EXE 8 /* Hide /proc/self/exe for the process */ #define TASK_PFA_TEST(name, func) \ static inline bool task_##func(struct task_struct *p) \ @@ -1832,6 +1833,10 @@ TASK_PFA_CLEAR(SPEC_IB_DISABLE, spec_ib_disable) TASK_PFA_TEST(SPEC_IB_FORCE_DISABLE, spec_ib_force_disable) TASK_PFA_SET(SPEC_IB_FORCE_DISABLE, spec_ib_force_disable) +TASK_PFA_TEST(HIDE_SELF_EXE, hide_self_exe) +TASK_PFA_SET(HIDE_SELF_EXE, hide_self_exe) +TASK_PFA_CLEAR(HIDE_SELF_EXE, hide_self_exe) + static inline void current_restore_flags(unsigned long orig_flags, unsigned long flags) { diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index a5e06dcbba13..f12f3df12468 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -284,4 +284,7 @@ struct prctl_mm_map { #define PR_SET_VMA 0x53564d41 # define PR_SET_VMA_ANON_NAME 0 +#define PR_SET_HIDE_SELF_EXE 65 +#define PR_GET_HIDE_SELF_EXE 66 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index 5fd54bf0e886..e992f1b72973 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2626,6 +2626,15 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, case PR_SET_VMA: error = prctl_set_vma(arg2, arg3, arg4, arg5); break; + case PR_SET_HIDE_SELF_EXE: + if (arg2 != 1 || arg3 || arg4 || arg5) + return -EINVAL; + task_set_hide_self_exe(current); + break; + case PR_GET_HIDE_SELF_EXE: + if (arg2 || arg3 || arg4 || arg5) + return -EINVAL; + return task_hide_self_exe(current) ? 1 : 0; default: error = -EINVAL; break; diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/prctl.h index a5e06dcbba13..f12f3df12468 100644 --- a/tools/include/uapi/linux/prctl.h +++ b/tools/include/uapi/linux/prctl.h @@ -284,4 +284,7 @@ struct prctl_mm_map { #define PR_SET_VMA 0x53564d41 # define PR_SET_VMA_ANON_NAME 0 +#define PR_SET_HIDE_SELF_EXE 65 +#define PR_GET_HIDE_SELF_EXE 66 + #endif /* _LINUX_PRCTL_H */ From patchwork Fri Jan 20 10:25:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Giuseppe Scrivano X-Patchwork-Id: 46284 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:adf:eb09:0:0:0:0:0 with SMTP id s9csp121182wrn; Fri, 20 Jan 2023 02:30:34 -0800 (PST) X-Google-Smtp-Source: AMrXdXvqXL+APZFFkKQqqkpTvefoeAkzw8S/nJ+fXl8p3Ix38cSkJ7R6HNXeJf3bFyCmMk8UmXBQ X-Received: by 2002:a17:903:428b:b0:192:feeb:b06d with SMTP id ju11-20020a170903428b00b00192feebb06dmr34812147plb.62.1674210634377; Fri, 20 Jan 2023 02:30:34 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1674210634; cv=none; d=google.com; s=arc-20160816; b=oduoYGeEndZwVl2U+cGVjluCLgmgVSjgbAqHpsw/NFp1pUdC3BHDUaU0aoRaT/xKAi YRelqpYI7SpkTkIRYHA3qqwl1J5c16mFRrEEObee9JeDpngaePOXhqcE254AulzaCnSX RtubSuWC9FfKEjTatK05gXqRmBniPoT60FeY2KJJpxcqj5y2eLZbSm0LiqLNiW7+5FUw 9EZKPaZj/UW04+SQ9r9AArAWZaR33OEMxaFdyYi3HwAHRKjiZ6Me2WAmri4FkTkBbCbx +TTv/thIgTf/sur2Xxgy/Vsg/inw7iFnt4aXx5yImgmpoQEOsBmlmiYXYDrrget7z7fL io0w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature; bh=rEadMCAXQIh3KzHbjItpcUECeNN2632kxRUh1w4pwmU=; b=DBuRqgyWt6Tl6gmMv6BAZzehNqr+t8FfpDiuBDKMUHTb03ST82BiJMznRCyzqF4D+Z r9EgQs0di63jy6h9pf3W4/eaDQ7uz1ai32S44J+RfCd3Ib1H6tIJfg7o43MMWdLqpc0y l062un2G+YU9aHZ7li5QtRGS44By8U9QkUbcPDo5/v+GL+3JDuDpOaVI7tTMiAs4eyIJ 2Ft4nRCvxb16BtpiAkpg2wgkynRozER3ULFEn+5hrErVeOXfnPxlEcuKMiwtfECqmqWc ucS5U2Wh+CKni3Yh+fO7711eSUVCTAjgmsldE3dmbiYzKQj3zTD47vOChH04DGLXtwx8 8ZPQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=Lut6FVmb; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from out1.vger.email (out1.vger.email. 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Fri, 20 Jan 2023 10:25:36 +0000 (UTC) Received: from lithium.redhat.com (unknown [10.39.194.249]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7C51053AA; Fri, 20 Jan 2023 10:25:34 +0000 (UTC) From: Giuseppe Scrivano To: linux-kernel@vger.kernel.org Cc: keescook@chromium.org, bristot@redhat.com, ebiederm@xmission.com, brauner@kernel.org, cyphar@cyphar.com, viro@zeniv.linux.org.uk, alexl@redhat.com, peterz@infradead.org, bmasney@redhat.com, gscrivan@redhat.com Subject: [PATCH v3 2/2] selftests: add tests for prctl(SET_HIDE_SELF_EXE) Date: Fri, 20 Jan 2023 11:25:12 +0100 Message-Id: <20230120102512.3195094-2-gscrivan@redhat.com> In-Reply-To: <20230120102512.3195094-1-gscrivan@redhat.com> References: <20230120102512.3195094-1-gscrivan@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1755537090467301554?= X-GMAIL-MSGID: =?utf-8?q?1755537090467301554?= Signed-off-by: Giuseppe Scrivano Reviewed-by: Brian Masney --- tools/testing/selftests/prctl/Makefile | 2 +- tools/testing/selftests/prctl/hide-self-exe.c | 114 ++++++++++++++++++ 2 files changed, 115 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/prctl/hide-self-exe.c diff --git a/tools/testing/selftests/prctl/Makefile b/tools/testing/selftests/prctl/Makefile index c7923b205222..024e107b26ec 100644 --- a/tools/testing/selftests/prctl/Makefile +++ b/tools/testing/selftests/prctl/Makefile @@ -5,7 +5,7 @@ ARCH ?= $(shell echo $(uname_M) | sed -e s/i.86/x86/ -e s/x86_64/x86/) ifeq ($(ARCH),x86) TEST_PROGS := disable-tsc-ctxt-sw-stress-test disable-tsc-on-off-stress-test \ - disable-tsc-test + disable-tsc-test hide-self-exe all: $(TEST_PROGS) include ../lib.mk diff --git a/tools/testing/selftests/prctl/hide-self-exe.c b/tools/testing/selftests/prctl/hide-self-exe.c new file mode 100644 index 000000000000..da129c5d736d --- /dev/null +++ b/tools/testing/selftests/prctl/hide-self-exe.c @@ -0,0 +1,114 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Tests for prctl(PR_GET_HIDE_SELF_EXE, ...) / prctl(PR_SET_HIDE_SELF_EXE, ...) + * + */ + +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#ifndef PR_SET_HIDE_SELF_EXE +# define PR_SET_HIDE_SELF_EXE 65 +# define PR_GET_HIDE_SELF_EXE 66 +#endif + +int main(void) +{ + int status; + pid_t pid; + int ret; + + ret = open("/proc/self/exe", O_RDONLY); + if (ret < 0) { + perror("open /proc/self/exe"); + exit(EXIT_FAILURE); + } + close(ret); + + ret = prctl(PR_GET_HIDE_SELF_EXE, 0, 0, 0, 0); + if (ret != 0) { + perror("prctl(PR_GET_HIDE_SELF_EXE)"); + exit(EXIT_FAILURE); + } + + ret = prctl(PR_SET_HIDE_SELF_EXE, 1, 0, 0, 0); + if (ret != 0) { + perror("prctl(PR_SET_HIDE_SELF_EXE)"); + exit(EXIT_FAILURE); + } + + /* check it doesn't fail a second time. */ + ret = prctl(PR_SET_HIDE_SELF_EXE, 1, 0, 0, 0); + if (ret != 0) { + perror("prctl(PR_SET_HIDE_SELF_EXE)"); + exit(EXIT_FAILURE); + } + + ret = prctl(PR_GET_HIDE_SELF_EXE, 0, 0, 0, 0); + if (ret != 1) { + perror("prctl(PR_GET_HIDE_SELF_EXE)"); + exit(EXIT_FAILURE); + } + + ret = open("/proc/self/exe", O_RDONLY); + if (ret >= 0 || errno != ENOENT) { + perror("open /proc/self/exe succeeded"); + exit(EXIT_FAILURE); + } + + pid = fork(); + if (pid < 0) { + perror("fork"); + exit(EXIT_FAILURE); + } + if (pid == 0) { + /* It cannot be unset after a fork(). */ + ret = prctl(PR_SET_HIDE_SELF_EXE, 0, 0, 0, 0); + if (ret == 0) { + perror("prctl(PR_SET_HIDE_SELF_EXE)"); + exit(EXIT_FAILURE); + } + + /* The getter still return the correct value. */ + ret = prctl(PR_GET_HIDE_SELF_EXE, 0, 0, 0, 0); + if (ret != 1) { + perror("prctl(PR_GET_HIDE_SELF_EXE)"); + exit(EXIT_FAILURE); + } + + /* It must be unreachable after fork(). */ + ret = open("/proc/self/exe", O_RDONLY); + if (ret >= 0 || errno != ENOENT) + exit(EXIT_FAILURE); + close(ret); + + /* It can be set again. */ + ret = prctl(PR_SET_HIDE_SELF_EXE, 1, 0, 0, 0); + if (ret != 0) { + perror("prctl(PR_SET_HIDE_SELF_EXE)"); + exit(EXIT_FAILURE); + } + + /* HIDE_SELF_EXE is cleared after execve. */ + ret = system("cat /proc/self/exe > /dev/null"); + exit(ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE); + } + if (waitpid(pid, &status, 0) != pid) { + perror("waitpid"); + exit(EXIT_FAILURE); + } + if (status != 0) { + perror("child failed"); + exit(EXIT_FAILURE); + } + exit(EXIT_SUCCESS); +}