/proc/pid/status: add "Seccomp" field

It is currently impossible to examine the state of seccomp for a given
process.  While attaching with gdb and attempting "call
prctl(PR_GET_SECCOMP,...)" will work with some situations, it is not
reliable.  If the process is in seccomp mode 1, this query will kill the
process (prctl not allowed), if the process is in mode 2 with prctl not
allowed, it will similarly be killed, and in weird cases, if prctl is
filtered to return errno 0, it can look like seccomp is disabled.

When reviewing the state of running processes, there should be a way to
externally examine the seccomp mode.  ("Did this build of Chrome end up
using seccomp?" "Did my distro ship ssh with seccomp enabled?")

This adds the "Seccomp" line to /proc/$pid/status.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: James Morris <jmorris@namei.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 377a37366dde..077235ffb38b 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -336,6 +336,13 @@ static inline void task_cap(struct seq_file *m, struct task_struct *p)
         render_cap_t(m, "CapBnd:\t", &cap_bset);
 }
 
+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
+}
+
 static inline void task_context_switch_counts(struct seq_file *m,
                                                 struct task_struct *p)
 {
@@ -369,6 +376,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
         }
         task_sig(m, task);
         task_cap(m, task);
+        task_seccomp(m, task);
         task_cpus_allowed(m, task);
         cpuset_task_status_allowed(m, task);
         task_context_switch_counts(m, task);