[PATCH v2] kernel/trace: Fix cleanup logic of enable_trace_eprobe

[Tzvetomir Stoyanov (VMware)]

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.

Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events")
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx>
---
v2: Added one-time warning, as suggested by Steven Rostedt.

 kernel/trace/trace_eprobe.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index 67e854979d53..6629fa217c99 100644
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -702,8 +702,18 @@ static int enable_trace_eprobe(struct trace_event_call *call,
 
 	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 (file)
 			trace_probe_remove_file(tp, file);
 		else
-- 
2.41.0