tracing: Disable "other" permission bits in the tracefs files

When building the files in the tracefs file system, do not by default set
any permissions for OTH (other). This will make it easier for admins who
want to define a group for accessing tracefs and not having to first
disable all the permission bits for "other" in the file system.

As tracing can leak sensitive information, it should never by default
allowing all users access. An admin can still set the permission bits for
others to have access, which may be useful for creating a honeypot and
seeing who takes advantage of it and roots the machine.

Link: https://lkml.kernel.org/r/20210818153038.864149276@goodmis.org

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 22 insertions, 20 deletions

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index bf54d2803261..4021b9a79f93 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -2312,7 +2312,8 @@ event_subsystem_dir(struct trace_array *tr, const char *name,
 	/* the ftrace system is special, do not create enable or filter files */
 	if (strcmp(name, "ftrace") != 0) {
 
-		entry = tracefs_create_file("filter", 0644, dir->entry, dir,
+		entry = tracefs_create_file("filter", TRACE_MODE_WRITE,
+					    dir->entry, dir,
 					    &ftrace_subsystem_filter_fops);
 		if (!entry) {
 			kfree(system->filter);
@@ -2320,7 +2321,7 @@ event_subsystem_dir(struct trace_array *tr, const char *name,
 			pr_warn("Could not create tracefs '%s/filter' entry\n", name);
 		}
 
-		trace_create_file("enable", 0644, dir->entry, dir,
+		trace_create_file("enable", TRACE_MODE_WRITE, dir->entry, dir,
 				  &ftrace_system_enable_fops);
 	}
 
@@ -2402,12 +2403,12 @@ event_create_dir(struct dentry *parent, struct trace_event_file *file)
 	}
 
 	if (call->class->reg && !(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE))
-		trace_create_file("enable", 0644, file->dir, file,
+		trace_create_file("enable", TRACE_MODE_WRITE, file->dir, file,
 				  &ftrace_enable_fops);
 
 #ifdef CONFIG_PERF_EVENTS
 	if (call->event.type && call->class->reg)
-		trace_create_file("id", 0444, file->dir,
+		trace_create_file("id", TRACE_MODE_READ, file->dir,
 				  (void *)(long)call->event.type,
 				  &ftrace_event_id_fops);
 #endif
@@ -2423,22 +2424,22 @@ event_create_dir(struct dentry *parent, struct trace_event_file *file)
 	 * triggers or filters.
 	 */
 	if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)) {
-		trace_create_file("filter", 0644, file->dir, file,
-				  &ftrace_event_filter_fops);
+		trace_create_file("filter", TRACE_MODE_WRITE, file->dir,
+				  file, &ftrace_event_filter_fops);
 
-		trace_create_file("trigger", 0644, file->dir, file,
-				  &event_trigger_fops);
+		trace_create_file("trigger", TRACE_MODE_WRITE, file->dir,
+				  file, &event_trigger_fops);
 	}
 
 #ifdef CONFIG_HIST_TRIGGERS
-	trace_create_file("hist", 0444, file->dir, file,
+	trace_create_file("hist", TRACE_MODE_READ, file->dir, file,
 			  &event_hist_fops);
 #endif
 #ifdef CONFIG_HIST_TRIGGERS_DEBUG
-	trace_create_file("hist_debug", 0444, file->dir, file,
+	trace_create_file("hist_debug", TRACE_MODE_READ, file->dir, file,
 			  &event_hist_debug_fops);
 #endif
-	trace_create_file("format", 0444, file->dir, call,
+	trace_create_file("format", TRACE_MODE_READ, file->dir, call,
 			  &ftrace_event_format_fops);
 
 #ifdef CONFIG_TRACE_EVENT_INJECT
@@ -3433,7 +3434,7 @@ create_event_toplevel_files(struct dentry *parent, struct trace_array *tr)
 	struct dentry *d_events;
 	struct dentry *entry;
 
-	entry = tracefs_create_file("set_event", 0644, parent,
+	entry = tracefs_create_file("set_event", TRACE_MODE_WRITE, parent,
 				    tr, &ftrace_set_event_fops);
 	if (!entry) {
 		pr_warn("Could not create tracefs 'set_event' entry\n");
@@ -3446,7 +3447,7 @@ create_event_toplevel_files(struct dentry *parent, struct trace_array *tr)
 		return -ENOMEM;
 	}
 
-	entry = trace_create_file("enable", 0644, d_events,
+	entry = trace_create_file("enable", TRACE_MODE_WRITE, d_events,
 				  tr, &ftrace_tr_enable_fops);
 	if (!entry) {
 		pr_warn("Could not create tracefs 'enable' entry\n");
@@ -3455,24 +3456,25 @@ create_event_toplevel_files(struct dentry *parent, struct trace_array *tr)
 
 	/* There are not as crucial, just warn if they are not created */
 
-	entry = tracefs_create_file("set_event_pid", 0644, parent,
+	entry = tracefs_create_file("set_event_pid", TRACE_MODE_WRITE, parent,
 				    tr, &ftrace_set_event_pid_fops);
 	if (!entry)
 		pr_warn("Could not create tracefs 'set_event_pid' entry\n");
 
-	entry = tracefs_create_file("set_event_notrace_pid", 0644, parent,
-				    tr, &ftrace_set_event_notrace_pid_fops);
+	entry = tracefs_create_file("set_event_notrace_pid",
+				    TRACE_MODE_WRITE, parent, tr,
+				    &ftrace_set_event_notrace_pid_fops);
 	if (!entry)
 		pr_warn("Could not create tracefs 'set_event_notrace_pid' entry\n");
 
 	/* ring buffer internal formats */
-	entry = trace_create_file("header_page", 0444, d_events,
+	entry = trace_create_file("header_page", TRACE_MODE_READ, d_events,
 				  ring_buffer_print_page_header,
 				  &ftrace_show_header_fops);
 	if (!entry)
 		pr_warn("Could not create tracefs 'header_page' entry\n");
 
-	entry = trace_create_file("header_event", 0444, d_events,
+	entry = trace_create_file("header_event", TRACE_MODE_READ, d_events,
 				  ring_buffer_print_entry_header,
 				  &ftrace_show_header_fops);
 	if (!entry)
@@ -3689,8 +3691,8 @@ __init int event_trace_init(void)
 	if (!tr)
 		return -ENODEV;
 
-	entry = tracefs_create_file("available_events", 0444, NULL,
-				    tr, &ftrace_avail_fops);
+	entry = tracefs_create_file("available_events", TRACE_MODE_READ,
+				    NULL, tr, &ftrace_avail_fops);
 	if (!entry)
 		pr_warn("Could not create tracefs 'available_events' entry\n");