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Message-Id: <20230310112554.1261731-3-gscrivan@redhat.com>
Date: Fri, 10 Mar 2023 12:25:54 +0100
From: Giuseppe Scrivano <gscrivan@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: keescook@...omium.org, bristot@...hat.com, ebiederm@...ssion.com,
brauner@...nel.org, cyphar@...har.com, viro@...iv.linux.org.uk,
walters@...bum.org, avagin@...il.com, alexl@...hat.com,
peterz@...radead.org, bmasney@...hat.com, gscrivan@...hat.com
Subject: [PATCH v4 3/3] selftests: add tests for prctl(SET_HIDE_SELF_EXE)
Signed-off-by: Giuseppe Scrivano <gscrivan@...hat.com>
---
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 <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <linux/prctl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#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);
+}
--
2.39.2
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