UBUNTU: SAUCE: proc: Provide details on speculation flaw mitigations

CVE-2018-3639 (x86)

As done with seccomp and no_new_privs, also show speculation flaw
mitigation state in /proc/$pid/status.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
[juergh:
 - Context adjustments.
 - Include linux/nospec.h to prevent compilation error.]
Signed-off-by: Juerg Haefliger <juergh@canonical.com>

fs/proc/array.c

@@ -79,6 +79,8 @@
 #include <linux/delayacct.h>
 #include <linux/seq_file.h>
 #include <linux/pid_namespace.h>
+#include <linux/nospec.h>
+#include <linux/prctl.h>
 #include <linux/ptrace.h>
 #include <linux/tracehook.h>
 #include <linux/string_helpers.h>
@@ -332,6 +334,28 @@ static inline void task_seccomp(struct seq_file *m, struct task_struct *p)
 #ifdef CONFIG_SECCOMP
 	seq_printf(m, "Seccomp:\t%d\n", p->seccomp.mode);
 #endif
+	seq_printf(m, "\nSpeculation Store Bypass:\t");
+	switch (arch_prctl_spec_ctrl_get(p, PR_SPEC_STORE_BYPASS)) {
+	case -EINVAL:
+		seq_printf(m, "unknown");
+		break;
+	case PR_SPEC_NOT_AFFECTED:
+		seq_printf(m, "not vulnerable");
+		break;
+	case PR_SPEC_PRCTL | PR_SPEC_DISABLE:
+		seq_printf(m, "thread mitigated");
+		break;
+	case PR_SPEC_PRCTL | PR_SPEC_ENABLE:
+		seq_printf(m, "thread vulnerable");
+		break;
+	case PR_SPEC_DISABLE:
+		seq_printf(m, "globally mitigated");
+		break;
+	default:
+		seq_printf(m, "vulnerable");
+		break;
+	}
+	seq_putc(m, '\n');
 }
 
 static inline void task_context_switch_counts(struct seq_file *m,