userns: Teach trace to use from_kuid

- When tracing capture the kuid.
- When displaying the data to user space convert the kuid into the
  user namespace of the process that opened the report file.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

2 files changed, 3 insertions, 2 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5c38c81496ce..c9ace838d509 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2060,7 +2060,8 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
         seq_puts(m, "#    -----------------\n");
         seq_printf(m, "#    | task: %.16s-%d "
                    "(uid:%d nice:%ld policy:%ld rt_prio:%ld)\n",
-                   data->comm, data->pid, data->uid, data->nice,
+                   data->comm, data->pid,
+                   from_kuid_munged(seq_user_ns(m), data->uid), data->nice,
                    data->policy, data->rt_priority);
         seq_puts(m, "#    -----------------\n");
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 55e1f7f0db12..40a6f30c985f 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -147,7 +147,7 @@ struct trace_array_cpu {
         unsigned long           skipped_entries;
         cycle_t                 preempt_timestamp;
         pid_t                   pid;
-        uid_t                   uid;
+        kuid_t                  uid;
         char                    comm[TASK_COMM_LEN];
 };