@@ -1,6 +1,6 @@
# SPDX-License-Identifier: GPL-2.0-only
-CFLAGS += -iquote../../../../include/uapi -Wall
+CFLAGS += -std=c99 -pthread -iquote../../../../include/uapi -Wall
-TEST_GEN_PROGS := get_syscall_info peeksiginfo
+TEST_GEN_PROGS := get_syscall_info peeksiginfo vmaccess
include ../lib.mk
new file mode 100644
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2020 Bernd Edlinger <bernd.edlinger@hotmail.de>
+ * All rights reserved.
+ *
+ * Check whether /proc/$pid/mem can be accessed without causing deadlocks
+ * when de_thread is blocked with ->cred_guard_mutex held.
+ */
+
+#include "../kselftest_harness.h"
+#include <stdio.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/ptrace.h>
+
+static void *thread(void *arg)
+{
+ ptrace(PTRACE_TRACEME, 0, 0L, 0L);
+ return NULL;
+}
+
+TEST(vmaccess)
+{
+ int f, pid = fork();
+ char mm[64];
+
+ if (!pid) {
+ pthread_t pt;
+
+ pthread_create(&pt, NULL, thread, NULL);
+ pthread_join(pt, NULL);
+ execlp("true", "true", NULL);
+ }
+
+ sleep(1);
+ sprintf(mm, "/proc/%d/mem", pid);
+ f = open(mm, O_RDONLY);
+ ASSERT_GE(f, 0);
+ close(f);
+ f = kill(pid, SIGCONT);
+ ASSERT_EQ(f, 0);
+}
+
+TEST(attach)
+{
+ int s, k, pid = fork();
+
+ if (!pid) {
+ pthread_t pt;
+
+ pthread_create(&pt, NULL, thread, NULL);
+ pthread_join(pt, NULL);
+ execlp("sleep", "sleep", "2", NULL);
+ }
+
+ sleep(1);
+ k = ptrace(PTRACE_ATTACH, pid, 0L, 0L);
+ ASSERT_EQ(errno, EAGAIN);
+ ASSERT_EQ(k, -1);
+ k = waitpid(-1, &s, WNOHANG);
+ ASSERT_NE(k, -1);
+ ASSERT_NE(k, 0);
+ ASSERT_NE(k, pid);
+ ASSERT_EQ(WIFEXITED(s), 1);
+ ASSERT_EQ(WEXITSTATUS(s), 0);
+ sleep(1);
+ k = ptrace(PTRACE_ATTACH, pid, 0L, 0L);
+ ASSERT_EQ(k, 0);
+ k = waitpid(-1, &s, 0);
+ ASSERT_EQ(k, pid);
+ ASSERT_EQ(WIFSTOPPED(s), 1);
+ ASSERT_EQ(WSTOPSIG(s), SIGSTOP);
+ k = ptrace(PTRACE_DETACH, pid, 0L, 0L);
+ ASSERT_EQ(k, 0);
+ k = waitpid(-1, &s, 0);
+ ASSERT_EQ(k, pid);
+ ASSERT_EQ(WIFEXITED(s), 1);
+ ASSERT_EQ(WEXITSTATUS(s), 0);
+ k = waitpid(-1, NULL, 0);
+ ASSERT_EQ(k, -1);
+ ASSERT_EQ(errno, ECHILD);
+}
+
+TEST_HARNESS_MAIN
This adds test cases for ptrace deadlocks. Additionally fixes a compile problem in get_syscall_info.c, observed with gcc-4.8.4: get_syscall_info.c: In function 'get_syscall_info': get_syscall_info.c:93:3: error: 'for' loop initial declarations are only allowed in C99 mode for (unsigned int i = 0; i < ARRAY_SIZE(args); ++i) { ^ get_syscall_info.c:93:3: note: use option -std=c99 or -std=gnu99 to compile your code Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de> Reviewed-by: Kees Cook <keescook@chromium.org> --- tools/testing/selftests/ptrace/Makefile | 4 +- tools/testing/selftests/ptrace/vmaccess.c | 86 +++++++++++++++++++++++++++++++ 2 files changed, 88 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/ptrace/vmaccess.c