Add test for CVE 2018-8897

Fixes #594

Signed-off-by: Martin Doucha <mdoucha@suse.cz>
Reviewed-by: Cyril Hrubis <metan@ucw.cz>

2 files changed, 104 insertions, 0 deletions

diff --git a/testcases/kernel/syscalls/ptrace/.gitignore b/testcases/kernel/syscalls/ptrace/.gitignore
index 301e2f564..7639e1a9f 100644
--- a/testcases/kernel/syscalls/ptrace/.gitignore
+++ b/testcases/kernel/syscalls/ptrace/.gitignore
@@ -4,3 +4,4 @@
 /ptrace05
 /ptrace07
 /ptrace08
+/ptrace09
diff --git a/testcases/kernel/syscalls/ptrace/ptrace09.c b/testcases/kernel/syscalls/ptrace/ptrace09.c
new file mode 100644
index 000000000..85875ce65
--- /dev/null
+++ b/testcases/kernel/syscalls/ptrace/ptrace09.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2018 SUSE LLC <nstange@suse.de>
+ * Copyright (C) 2020 SUSE LLC <mdoucha@suse.cz>
+ *
+ * CVE-2018-8897
+ *
+ * Test that the MOV SS instruction touching a ptrace watchpoint followed by
+ * INT3 breakpoint is handled correctly by the kernel. Kernel crash fixed in:
+ *
+ *  commit d8ba61ba58c88d5207c1ba2f7d9a2280e7d03be9
+ *  Author: Andy Lutomirski <luto@kernel.org>
+ *  Date:   Thu Jul 23 15:37:48 2015 -0700
+ *
+ *  x86/entry/64: Don't use IST entry for #BP stack
+ */
+
+#include <stdlib.h>
+#include <stddef.h>
+#include <sys/ptrace.h>
+#include <sys/user.h>
+#include <signal.h>
+#include "tst_test.h"
+
+#if defined(__i386__) || defined(__x86_64__)
+static short watchpoint;
+static pid_t child_pid;
+
+static int child_main(void)
+{
+	SAFE_PTRACE(PTRACE_TRACEME, 0, NULL, NULL);
+	raise(SIGSTOP);
+	/* wait for SIGCONT from parent */
+
+	asm volatile(
+		"mov %%ss, %0\n"
+		"mov %0, %%ss\n"
+		"int $3\n"
+		: "+m" (watchpoint)
+	);
+
+	return 0;
+}
+
+static void run(void)
+{
+	int status;
+
+	child_pid = SAFE_FORK();
+
+	if (!child_pid) {
+		exit(child_main());
+	}
+
+	if (SAFE_WAITPID(child_pid, &status, 0) != child_pid)
+		tst_brk(TBROK, "Received event from unexpected PID");
+
+	SAFE_PTRACE(PTRACE_POKEUSER, child_pid,
+		(void *)offsetof(struct user, u_debugreg[0]), &watchpoint);
+	SAFE_PTRACE(PTRACE_POKEUSER, child_pid,
+		(void *)offsetof(struct user, u_debugreg[7]), (void *)0x30001);
+	SAFE_PTRACE(PTRACE_CONT, child_pid, NULL, NULL);
+
+	while (1) {
+		if (SAFE_WAITPID(child_pid, &status, 0) != child_pid)
+			tst_brk(TBROK, "Received event from unexpected PID");
+
+		if (WIFEXITED(status)) {
+			child_pid = 0;
+			break;
+		}
+
+		if (WIFSTOPPED(status)) {
+			SAFE_PTRACE(PTRACE_CONT, child_pid, NULL, NULL);
+			continue;
+		}
+
+		tst_brk(TBROK, "Unexpected event from child");
+	}
+
+	tst_res(TPASS, "We're still here. Nothing bad happened, probably.");
+}
+
+static void cleanup(void)
+{
+	/* Main process terminated by tst_brk() with child still paused */
+	if (child_pid)
+		SAFE_KILL(child_pid, SIGKILL);
+}
+
+static struct tst_test test = {
+	.test_all = run,
+	.cleanup = cleanup,
+	.forks_child = 1,
+	.tags = (const struct tst_tag[]) {
+		{"linux-git", "d8ba61ba58c8"},
+		{"CVE", "2018-8897"},
+		{}
+	}
+};
+#else
+TST_TEST_TCONF("This test is only supported on x86 systems");
+#endif