[PATCH 3.16 018/131] proc: Provide details on speculation flaw mitigations

[Ben Hutchings]

3.16.59-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@xxxxxxxxxxxx>

commit fae1fa0fc6cca8beee3ab8ed71d54f9a78fa3f64 upstream.

As done with seccomp and no_new_privs, also show speculation flaw
mitigation state in /proc/$pid/status.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/proc/array.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -79,6 +79,7 @@
 #include <linux/delayacct.h>
 #include <linux/seq_file.h>
 #include <linux/pid_namespace.h>
+#include <linux/prctl.h>
 #include <linux/ptrace.h>
 #include <linux/tracehook.h>
 #include <linux/user_namespace.h>
@@ -326,6 +327,28 @@ static inline void task_seccomp(struct s
 #ifdef CONFIG_SECCOMP
 	seq_printf(m, "Seccomp:\t%d\n", p->seccomp.mode);
 #endif
+	seq_printf(m, "Speculation 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,