[RFC PATCH] tracing/user_events: Limit showing event names to CAP_SYS_ADMIN users

[Beau Belgrave <beaub@linux.microsoft.com>]

Show actual names only to CAP_SYS_ADMIN capable users.

When user_events are configured to have broader write access than
default, this allows seeing names of events from other containers, etc.
Limit who can see the actual names to prevent event squatting or
information leakage.

Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
---
 kernel/trace/trace_events_user.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 2b5e9fdb63a0..fb9fb2071173 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1480,6 +1480,9 @@ static int user_seq_show(struct seq_file *m, void *p)
 	struct user_event *user;
 	char status;
 	int i, active = 0, busy = 0, flags;
+	bool show_names;
+
+	show_names = capable(CAP_SYS_ADMIN);
 
 	mutex_lock(&reg_mutex);
 
@@ -1487,7 +1490,10 @@ static int user_seq_show(struct seq_file *m, void *p)
 		status = register_page_data[user->index];
 		flags = user->flags;
 
-		seq_printf(m, "%d:%s", user->index, EVENT_NAME(user));
+		if (show_names)
+			seq_printf(m, "%d:%s", user->index, EVENT_NAME(user));
+		else
+			seq_printf(m, "%d:<hidden>", user->index);
 
 		if (flags != 0 || status != 0)
 			seq_puts(m, " #");

base-commit: 864ea0e10cc90416a01b46f0d47a6f26dc020820
-- 
2.17.1