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Fri, 10 Mar 2023 11:26:15 +0000 (UTC) Received: from carbon.redhat.com (unknown [10.39.194.146]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8A9F0C15BAD; Fri, 10 Mar 2023 11:26:12 +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, walters@verbum.org, avagin@gmail.com, alexl@redhat.com, peterz@infradead.org, bmasney@redhat.com, gscrivan@redhat.com Subject: [PATCH v4 3/3] selftests: add tests for prctl(SET_HIDE_SELF_EXE) Date: Fri, 10 Mar 2023 12:25:54 +0100 Message-Id: <20230310112554.1261731-3-gscrivan@redhat.com> In-Reply-To: <20230310112554.1261731-1-gscrivan@redhat.com> References: <20230310112554.1261731-1-gscrivan@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 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,URIBL_BLOCKED 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?1759980037876891474?= X-GMAIL-MSGID: =?utf-8?q?1759980037876891474?= Signed-off-by: Giuseppe Scrivano --- tools/testing/selftests/prctl/Makefile | 2 +- tools/testing/selftests/prctl/hide-self-exe.c | 193 ++++++++++++++++++ 2 files changed, 194 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..d95a7671c1ab --- /dev/null +++ b/tools/testing/selftests/prctl/hide-self-exe.c @@ -0,0 +1,193 @@ +// 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 +#include + +#ifndef PR_SET_HIDE_SELF_EXE +# define PR_SET_HIDE_SELF_EXE 67 +# define PR_GET_HIDE_SELF_EXE 68 +#endif + +int main(void) +{ + char path[PATH_MAX]; + struct dirent *ent; + int status; + pid_t pid; + DIR *dir; + 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_SET_DUMPABLE, 0, 0, 0, 0); + if (ret != 0) { + perror("prctl(PR_SET_DUMPABLE, SUID_DUMP_DISABLE)"); + exit(EXIT_FAILURE); + } + + ret = prctl(PR_SET_DUMPABLE, 1, 0, 0, 0); + if (ret != 0) { + perror("prctl(PR_SET_DUMPABLE, SUID_DUMP_USER)"); + exit(EXIT_FAILURE); + } + + 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); + } + + ret = prctl(PR_GET_DUMPABLE, 0, 0, 0, 0); + if (ret != 1) { + perror("prctl(PR_GET_DUMPABLE)"); + exit(EXIT_FAILURE); + } + + ret = prctl(PR_SET_DUMPABLE, 0, 0, 0, 0); + if (ret != 0) { + perror("prctl(PR_SET_DUMPABLE, SUID_DUMP_DISABLE)"); + exit(EXIT_FAILURE); + } + + /* It is not permitted anymore. */ + ret = prctl(PR_SET_DUMPABLE, 1, 0, 0, 0); + if (ret == 0) { + perror("prctl(PR_SET_DUMPABLE, SUID_DUMP_USER)"); + exit(EXIT_FAILURE); + } + /* It can only be disabled. */ + ret = prctl(PR_SET_DUMPABLE, 0, 0, 0, 0); + if (ret != 0) { + perror("prctl(PR_SET_DUMPABLE, SUID_DUMP_DISABLE)"); + 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 != EPERM) { + perror("open /proc/self/exe succeeded"); + exit(EXIT_FAILURE); + } + + ret = execl("/proc/self/exe", "/proc/self/exe", NULL); + if (ret >= 0 || errno != EPERM) { + perror("execl /proc/self/exe succeeded or wrong error"); + 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 != EPERM) { + perror("open /proc/self/exe succeeded or wrong error"); + exit(EXIT_FAILURE); + } + + ret = execl("/proc/self/exe", "/proc/self/exe", NULL); + if (ret >= 0 || errno != EPERM) { + perror("execl /proc/self/exe succeeded wrong error"); + exit(EXIT_FAILURE); + } + + dir = opendir("/proc/self/map_files"); + if (dir == NULL) { + perror("opendir /proc/self/map_files"); + exit(EXIT_FAILURE); + } + + while ((ent = readdir(dir)) != NULL) { + if (ent->d_name[0] == '.') + continue; + + sprintf(path, "/proc/self/map_files/%s", ent->d_name); + ret = open(path, O_RDONLY); + if (ret >= 0 || errno != EPERM) { + perror("open /proc/self/map_files file succeeded or wrong error"); + exit(EXIT_FAILURE); + } + } + closedir(dir); + + /* 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); + } + + /* PR_SET_DUMPABLE must not be permitted. */ + ret = prctl(PR_SET_DUMPABLE, 1, 0, 0, 0); + if (ret == 0) { + perror("prctl(PR_SET_DUMPABLE, SUID_DUMP_USER)"); + 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); +}