kernel/trace: Fix cleanup logic of enable_trace_eprobe

The enable_trace_eprobe() function enables all event probes, attached
to given trace probe. If an error occurs in enabling one of the event
probes, all others should be roll backed. There is a bug in that roll
back logic - instead of all event probes, only the failed one is
disabled.

Link: https://lore.kernel.org/all/[email protected]/

Reported-by: Dan Carpenter <[email protected]>
Fixes: 7491e2c ("tracing: Add a probe that attaches to trace events")
Signed-off-by: Tzvetomir Stoyanov (VMware) <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>

Author: tzstoyanov

kernel/trace/trace_eprobe.c

@@ -675,6 +675,7 @@ static int enable_trace_eprobe(struct trace_event_call *call,
 	struct trace_eprobe *ep;
 	bool enabled;
 	int ret = 0;
+	int cnt = 0;
 
 	tp = trace_probe_primary_from_call(call);
 	if (WARN_ON_ONCE(!tp))
@@ -698,12 +699,25 @@ static int enable_trace_eprobe(struct trace_event_call *call,
 		if (ret)
 			break;
 		enabled = true;
+		cnt++;
 	}
 
 	if (ret) {
 		/* Failed to enable one of them. Roll back all */
-		if (enabled)
-			disable_eprobe(ep, file->tr);
+		if (enabled) {
+			/*
+			 * It's a bug if one failed for something other than memory
+			 * not being available but another eprobe succeeded.
+			 */
+			WARN_ON_ONCE(ret != -ENOMEM);
+
+			list_for_each_entry(pos, trace_probe_probe_list(tp), list) {
+				ep = container_of(pos, struct trace_eprobe, tp);
+				disable_eprobe(ep, file->tr);
+				if (!--cnt)
+					break;
+			}
+		}
 		if (file)
 			trace_probe_remove_file(tp, file);
 		else